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* eventfs: Do not use attributes for events directorySteven Rostedt (Google)2024-05-231-7/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | The top "events" directory has a static inode (it's created when it is and removed when the directory is removed). There's no need to use the events ei->attr to determine its permissions. But it is used for saving the permissions of the "events" directory for when it is created, as that is needed for the default permissions for the files and directories underneath it. For example: # cd /sys/kernel/tracing # mkdir instances/foo # chown 1001 instances/foo/events The files under instances/foo/events should still have the same owner as instances/foo (which the instances/foo/events ei->attr will hold), but the events directory now has owner 1001. Link: https://lore.kernel.org/lkml/20240522165032.104981011@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Cleanup permissions in creation of inodesSteven Rostedt (Google)2024-05-231-67/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The permissions being set during the creation of the inodes was updating eventfs_inode attributes as well. Those attributes should only be touched by the setattr or remount operations, not during the creation of inodes. The eventfs_inode attributes should only be used to set the inodes and should not be modified during the inode creation. Simplify the code and fix the situation by: 1) Removing the eventfs_find_events() and doing a simple lookup for the events descriptor in eventfs_get_inode() 2) Remove update_events_attr() as the attributes should only be used to update the inode and should not be modified here. 3) Add update_inode_attr() that uses the attributes to determine what the inode permissions should be. 4) As the parent_inode of the eventfs_root_inode structure is no longer needed, remove it. Now on creation, the inode gets the proper permissions without causing side effects to the ei->attr field. Link: https://lore.kernel.org/lkml/20240522165031.944088388@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Remove getattr and permission callbacksSteven Rostedt (Google)2024-05-231-40/+0
| | | | | | | | | | | | | | | | | | | | Now that inodes have their permissions updated on remount, the only other places to update the inode permissions are when they are created and in the setattr callback. The getattr and permission callbacks are not needed as the inodes should already be set at their proper settings. Remove the callbacks, as it not only simplifies the code, but also allows more flexibility to fix the inconsistencies with various corner cases (like changing the permission of an instance directory). Link: https://lore.kernel.org/lkml/20240522165031.782066021@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Consolidate the eventfs_inode update in eventfs_get_inode()Steven Rostedt (Google)2024-05-231-19/+23
| | | | | | | | | | | | | | | | To simplify the code, create a eventfs_get_inode() that is used when an eventfs file or directory is created. Have the internal tracefs_inode updated the appropriate flags in this function and update the inode's mode as well. Link: https://lore.kernel.org/lkml/20240522165031.624864160@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: Clear EVENT_INODE flag in tracefs_drop_inode()Steven Rostedt (Google)2024-05-231-16/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the inode is being dropped from the dentry, the TRACEFS_EVENT_INODE flag needs to be cleared to prevent a remount from calling eventfs_remount() on the tracefs_inode private data. There's a race between the inode is dropped (and the dentry freed) to where the inode is actually freed. If a remount happens between the two, the eventfs_inode could be accessed after it is freed (only the dentry keeps a ref count on it). Currently the TRACEFS_EVENT_INODE flag is cleared from the dentry iput() function. But this is incorrect, as it is possible that the inode has another reference to it. The flag should only be cleared when the inode is really being dropped and has no more references. That happens in the drop_inode callback of the inode, as that gets called when the last reference of the inode is released. Remove the tracefs_d_iput() function and move its logic to the more appropriate tracefs_drop_inode() callback function. Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.908205106@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Update all the eventfs_inodes from the events descriptorSteven Rostedt (Google)2024-05-231-13/+31
| | | | | | | | | | | | | | | | | | | | | | | | | | | | The change to update the permissions of the eventfs_inode had the misconception that using the tracefs_inode would find all the eventfs_inodes that have been updated and reset them on remount. The problem with this approach is that the eventfs_inodes are freed when they are no longer used (basically the reason the eventfs system exists). When they are freed, the updated eventfs_inodes are not reset on a remount because their tracefs_inodes have been freed. Instead, since the events directory eventfs_inode always has a tracefs_inode pointing to it (it is not freed when finished), and the events directory has a link to all its children, have the eventfs_remount() function only operate on the events eventfs_inode and have it descend into its children updating their uid and gids. Link: https://lore.kernel.org/all/CAK7LNARXgaWw3kH9JgrnH4vK6fr8LDkNKf3wq8NhMWJrVwJyVQ@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.754424703@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options") Reported-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: Update inode permissions on remountSteven Rostedt (Google)2024-05-232-7/+25
| | | | | | | | | | | | | | | | | When a remount happens, if a gid or uid is specified update the inodes to have the same gid and uid. This will allow the simplification of the permissions logic for the dynamically created files and directories. Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.592429986@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Keep the directories from having the same inode number as filesSteven Rostedt (Google)2024-05-231-1/+5
| | | | | | | | | | | | | | | | | The directories require unique inode numbers but all the eventfs files have the same inode number. Prevent the directories from having the same inode numbers as the files as that can confuse some tooling. Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.428826685@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Masahiro Yamada <masahiroy@kernel.org> Fixes: 834bf76add3e6 ("eventfs: Save directory inodes in the eventfs_inode structure") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* Merge tag 'trace-v6.10' of ↵Linus Torvalds2024-05-181-4/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing updates from Steven Rostedt: - Remove unused ftrace_direct_funcs variables - Fix a possible NULL pointer dereference race in eventfs - Update do_div() usage in trace event benchmark test - Speedup direct function registration with asynchronous RCU callback. The synchronization was done in the registration code and this caused delays when registering direct callbacks. Move the freeing to a call_rcu() that will prevent delaying of the registering. - Replace simple_strtoul() usage with kstrtoul() * tag 'trace-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: eventfs: Fix a possible null pointer dereference in eventfs_find_events() ftrace: Fix possible use-after-free issue in ftrace_location() ftrace: Remove unused global 'ftrace_direct_func_count' ftrace: Remove unused list 'ftrace_direct_funcs' tracing: Improve benchmark test performance by using do_div() ftrace: Use asynchronous grace period for register_ftrace_direct() ftrace: Replaces simple_strtoul in ftrace
| * eventfs: Fix a possible null pointer dereference in eventfs_find_events()Hao Ge2024-05-141-4/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In function eventfs_find_events,there is a potential null pointer that may be caused by calling update_events_attr which will perform some operations on the members of the ei struct when ei is NULL. Hence,When ei->is_freed is set,return NULL directly. Link: https://lore.kernel.org/linux-trace-kernel/20240513053338.63017-1-hao.ge@linux.dev Cc: stable@vger.kernel.org Fixes: 8186fff7ab64 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Hao Ge <gehao@kylinos.cn> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | Merge tag 'vfs-6.10.mount' of ↵Linus Torvalds2024-05-131-108/+94
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs Pull vfs mount API conversions from Christian Brauner: "This converts qnx6, minix, debugfs, tracefs, freevxfs, and openpromfs to the new mount api, further reducing the number of filesystems relying on the legacy mount api" * tag 'vfs-6.10.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: minix: convert minix to use the new mount api vfs: Convert tracefs to use the new mount API vfs: Convert debugfs to use the new mount API openpromfs: finish conversion to the new mount API freevxfs: Convert freevxfs to the new mount API. qnx6: convert qnx6 to use the new mount api
| * vfs: Convert tracefs to use the new mount APIDavid Howells2024-03-261-105/+91
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Convert the tracefs filesystem to the new internal mount API as the old one will be obsoleted and removed. This allows greater flexibility in communication of mount parameters between userspace, the VFS and the filesystem. See Documentation/filesystems/mount_api.txt for more information. Signed-off-by: David Howells <dhowells@redhat.com> Co-developed-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Eric Sandeen <sandeen@redhat.com> [sandeen: forward port to modern kernel, fix remounting] Link: https://lore.kernel.org/r/536e99d3-345c-448b-adee-a21389d7ab4b@redhat.com cc: Steven Rostedt <rostedt@goodmis.org> cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
* | eventfs: Have "events" directory get permissions from its parentSteven Rostedt (Google)2024-05-041-6/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The events directory gets its permissions from the root inode. But this can cause an inconsistency if the instances directory changes its permissions, as the permissions of the created directories under it should inherit the permissions of the instances directory when directories under it are created. Currently the behavior is: # cd /sys/kernel/tracing # chgrp 1002 instances # mkdir instances/foo # ls -l instances/foo [..] -r--r----- 1 root lkp 0 May 1 18:55 buffer_total_size_kb -rw-r----- 1 root lkp 0 May 1 18:55 current_tracer -rw-r----- 1 root lkp 0 May 1 18:55 error_log drwxr-xr-x 1 root root 0 May 1 18:55 events --w------- 1 root lkp 0 May 1 18:55 free_buffer drwxr-x--- 2 root lkp 0 May 1 18:55 options drwxr-x--- 10 root lkp 0 May 1 18:55 per_cpu -rw-r----- 1 root lkp 0 May 1 18:55 set_event All the files and directories under "foo" has the "lkp" group except the "events" directory. That's because its getting its default value from the mount point instead of its parent. Have the "events" directory make its default value based on its parent's permissions. That now gives: # ls -l instances/foo [..] -rw-r----- 1 root lkp 0 May 1 21:16 buffer_subbuf_size_kb -r--r----- 1 root lkp 0 May 1 21:16 buffer_total_size_kb -rw-r----- 1 root lkp 0 May 1 21:16 current_tracer -rw-r----- 1 root lkp 0 May 1 21:16 error_log drwxr-xr-x 1 root lkp 0 May 1 21:16 events --w------- 1 root lkp 0 May 1 21:16 free_buffer drwxr-x--- 2 root lkp 0 May 1 21:16 options drwxr-x--- 10 root lkp 0 May 1 21:16 per_cpu -rw-r----- 1 root lkp 0 May 1 21:16 set_event Link: https://lore.kernel.org/linux-trace-kernel/20240502200906.161887248@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 8186fff7ab649 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | eventfs: Do not treat events directory different than other directoriesSteven Rostedt (Google)2024-05-041-15/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Treat the events directory the same as other directories when it comes to permissions. The events directory was considered different because it's dentry is persistent, whereas the other directory dentries are created when accessed. But the way tracefs now does its ownership by using the root dentry's permissions as the default permissions, the events directory can get out of sync when a remount is performed setting the group and user permissions. Remove the special case for the events directory on setting the attributes. This allows the updates caused by remount to work properly as well as simplifies the code. Link: https://lore.kernel.org/linux-trace-kernel/20240502200906.002923579@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 8186fff7ab649 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | eventfs: Do not differentiate the toplevel events directorySteven Rostedt (Google)2024-05-042-25/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The toplevel events directory is really no different than the events directory of instances. Having the two be different caused inconsistencies and made it harder to fix the permissions bugs. Make all events directories act the same. Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.846448710@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 8186fff7ab649 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | tracefs: Still use mount point as default permissions for instancesSteven Rostedt (Google)2024-05-041-2/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If the instances directory's permissions were never change, then have it and its children use the mount point permissions as the default. Currently, the permissions of instance directories are determined by the instance directory's permissions itself. But if the tracefs file system is remounted and changes the permissions, the instance directory and its children should use the new permission. But because both the instance directory and its children use the instance directory's inode for permissions, it misses the update. To demonstrate this: # cd /sys/kernel/tracing/ # mkdir instances/foo # ls -ld instances/foo drwxr-x--- 5 root root 0 May 1 19:07 instances/foo # ls -ld instances drwxr-x--- 3 root root 0 May 1 18:57 instances # ls -ld current_tracer -rw-r----- 1 root root 0 May 1 18:57 current_tracer # mount -o remount,gid=1002 . # ls -ld instances drwxr-x--- 3 root root 0 May 1 18:57 instances # ls -ld instances/foo/ drwxr-x--- 5 root root 0 May 1 19:07 instances/foo/ # ls -ld current_tracer -rw-r----- 1 root lkp 0 May 1 18:57 current_tracer Notice that changing the group id to that of "lkp" did not affect the instances directory nor its children. It should have been: # ls -ld current_tracer -rw-r----- 1 root root 0 May 1 19:19 current_tracer # ls -ld instances/foo/ drwxr-x--- 5 root root 0 May 1 19:25 instances/foo/ # ls -ld instances drwxr-x--- 3 root root 0 May 1 19:19 instances # mount -o remount,gid=1002 . # ls -ld current_tracer -rw-r----- 1 root lkp 0 May 1 19:19 current_tracer # ls -ld instances drwxr-x--- 3 root lkp 0 May 1 19:19 instances # ls -ld instances/foo/ drwxr-x--- 5 root lkp 0 May 1 19:25 instances/foo/ Where all files were updated by the remount gid update. Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.686838327@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 8186fff7ab649 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | tracefs: Reset permissions on remount if permissions are optionsSteven Rostedt (Google)2024-05-043-2/+99
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's an inconsistency with the way permissions are handled in tracefs. Because the permissions are generated when accessed, they default to the root inode's permission if they were never set by the user. If the user sets the permissions, then a flag is set and the permissions are saved via the inode (for tracefs files) or an internal attribute field (for eventfs). But if a remount happens that specify the permissions, all the files that were not changed by the user gets updated, but the ones that were are not. If the user were to remount the file system with a given permission, then all files and directories within that file system should be updated. This can cause security issues if a file's permission was updated but the admin forgot about it. They could incorrectly think that remounting with permissions set would update all files, but miss some. For example: # cd /sys/kernel/tracing # chgrp 1002 current_tracer # ls -l [..] -rw-r----- 1 root root 0 May 1 21:25 buffer_size_kb -rw-r----- 1 root root 0 May 1 21:25 buffer_subbuf_size_kb -r--r----- 1 root root 0 May 1 21:25 buffer_total_size_kb -rw-r----- 1 root lkp 0 May 1 21:25 current_tracer -rw-r----- 1 root root 0 May 1 21:25 dynamic_events -r--r----- 1 root root 0 May 1 21:25 dyn_ftrace_total_info -r--r----- 1 root root 0 May 1 21:25 enabled_functions Where current_tracer now has group "lkp". # mount -o remount,gid=1001 . # ls -l -rw-r----- 1 root tracing 0 May 1 21:25 buffer_size_kb -rw-r----- 1 root tracing 0 May 1 21:25 buffer_subbuf_size_kb -r--r----- 1 root tracing 0 May 1 21:25 buffer_total_size_kb -rw-r----- 1 root lkp 0 May 1 21:25 current_tracer -rw-r----- 1 root tracing 0 May 1 21:25 dynamic_events -r--r----- 1 root tracing 0 May 1 21:25 dyn_ftrace_total_info -r--r----- 1 root tracing 0 May 1 21:25 enabled_functions Everything changed but the "current_tracer". Add a new link list that keeps track of all the tracefs_inodes which has the permission flags that tell if the file/dir should use the root inode's permission or not. Then on remount, clear all the flags so that the default behavior of using the root inode's permission is done for all files and directories. Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.529542160@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 8186fff7ab649 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | eventfs: Free all of the eventfs_inode after RCUSteven Rostedt (Google)2024-05-041-9/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The freeing of eventfs_inode via a kfree_rcu() callback. But the content of the eventfs_inode was being freed after the last kref. This is dangerous, as changes are being made that can access the content of an eventfs_inode from an RCU loop. Instead of using kfree_rcu() use call_rcu() that calls a function to do all the freeing of the eventfs_inode after a RCU grace period has expired. Link: https://lore.kernel.org/linux-trace-kernel/20240502200905.370261163@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Fixes: 43aa6f97c2d03 ("eventfs: Get rid of dentry pointers without refcounts") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | eventfs/tracing: Add callback for release of an eventfs_inodeSteven Rostedt (Google)2024-05-041-2/+21
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Synthetic events create and destroy tracefs files when they are created and removed. The tracing subsystem has its own file descriptor representing the state of the events attached to the tracefs files. There's a race between the eventfs files and this file descriptor of the tracing system where the following can cause an issue: With two scripts 'A' and 'B' doing: Script 'A': echo "hello int aaa" > /sys/kernel/tracing/synthetic_events while : do echo 0 > /sys/kernel/tracing/events/synthetic/hello/enable done Script 'B': echo > /sys/kernel/tracing/synthetic_events Script 'A' creates a synthetic event "hello" and then just writes zero into its enable file. Script 'B' removes all synthetic events (including the newly created "hello" event). What happens is that the opening of the "enable" file has: { struct trace_event_file *file = inode->i_private; int ret; ret = tracing_check_open_get_tr(file->tr); [..] But deleting the events frees the "file" descriptor, and a "use after free" happens with the dereference at "file->tr". The file descriptor does have a reference counter, but there needs to be a way to decrement it from the eventfs when the eventfs_inode is removed that represents this file descriptor. Add an optional "release" callback to the eventfs_entry array structure, that gets called when the eventfs file is about to be removed. This allows for the creating on the eventfs file to increment the tracing file descriptor ref counter. When the eventfs file is deleted, it can call the release function that will call the put function for the tracing file descriptor. This will protect the tracing file from being freed while a eventfs file that references it is being opened. Link: https://lore.kernel.org/linux-trace-kernel/20240426073410.17154-1-Tze-nan.Wu@mediatek.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240502090315.448cba46@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: Tze-nan wu <Tze-nan.Wu@mediatek.com> Tested-by: Tze-nan Wu (吳澤南) <Tze-nan.Wu@mediatek.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* | eventfs: Fix kernel-doc comments to functionsYang Li2024-04-111-4/+10
|/ | | | | | | | | | | This commit fix kernel-doc style comments with complete parameter descriptions for the lookup_file(),lookup_dir_entry() and lookup_file_dentry(). Link: https://lore.kernel.org/linux-trace-kernel/20240322062604.28862-1-yang.lee@linux.alibaba.com Signed-off-by: Yang Li <yang.lee@linux.alibaba.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Create eventfs_root_inode to store dentrySteven Rostedt (Google)2024-03-172-12/+55
| | | | | | | | | | | | | | | | | | | | Only the root "events" directory stores a dentry. There's no reason to hold a dentry pointer for every eventfs_inode as it is never set except for the root "events" eventfs_inode. Create a eventfs_root_inode structure that holds the events_dir dentry. The "events" eventfs_inode *is* special, let it have its own descriptor. Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.658992558@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Add WARN_ON_ONCE() to checks in eventfs_root_lookup()Steven Rostedt (Google)2024-03-171-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | There's a couple of if statements in eventfs_root_lookup() that should never be true. Instead of removing them, add WARN_ON_ONCE() around them. One is a tracefs_inode not being for eventfs. The other is a child being freed but still on the parent's children list. When a child is freed, it is removed from the list under the same mutex that is held during the iteration. Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/ Link: https://lore.kernel.org/linux-trace-kernel/20240201123346.724afa46@gandalf.local.home Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Reported-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* mm, slab: remove last vestiges of SLAB_MEM_SPREADLinus Torvalds2024-03-131-1/+0
| | | | | | | | | | | | | | Yes, yes, I know the slab people were planning on going slow and letting every subsystem fight this thing on their own. But let's just rip off the band-aid and get it over and done with. I don't want to see a number of unnecessary pull requests just to get rid of a flag that no longer has any meaning. This was mainly done with a couple of 'sed' scripts and then some manual cleanup of the end result. Link: https://lore.kernel.org/all/CAHk-=wji0u+OOtmAOD-5JV3SXcRJF___k_+8XNKmak0yd5vW1Q@mail.gmail.com/ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* eventfs: Keep all directory links at 1Steven Rostedt (Google)2024-02-011-4/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The directory link count in eventfs was somewhat bogus. It was only being updated when a directory child was being looked up and not on creation. One solution would be to update in get_attr() the link count by iterating the ei->children list and then adding 2. But that could slow down simple stat() calls, especially if it's done on all directories in eventfs. Another solution would be to add a parent pointer to the eventfs_inode and keep track of the number of sub directories it has on creation. But this adds overhead for something not really worthwhile. The solution decided upon is to keep all directory links in eventfs as 1. This tells user space not to rely on the hard links of directories. Which in this case it shouldn't. Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/ Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.339968298@goodmis.org Cc: stable@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Remove fsnotify*() functions from lookup()Steven Rostedt (Google)2024-02-011-2/+0
| | | | | | | | | | | | | | | | | | | | | The dentries and inodes are created when referenced in the lookup code. There's no reason to call fsnotify_*() functions when they are created by a reference. It doesn't make any sense. Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/ Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.166973329@goodmis.org Cc: stable@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Fixes: a376007917776 ("eventfs: Implement functions to create files and dirs when accessed"); Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Restructure eventfs_inode structure to be more condensedSteven Rostedt (Google)2024-02-011-15/+12
| | | | | | | | | | | | | | | | | Some of the eventfs_inode structure has holes in it. Rework the structure to be a bit more condensed, and also remove the no longer used llist field. Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.002321438@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Warn if an eventfs_inode is freed without is_freed being setSteven Rostedt (Google)2024-02-011-4/+14
| | | | | | | | | | | | | | | | | There should never be a case where an evenfs_inode is being freed without is_freed being set. Add a WARN_ON_ONCE() if it ever happens. That would mean there was one too many put_ei()s. Link: https://lore.kernel.org/linux-trace-kernel/20240201161616.843551963@goodmis.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Get rid of dentry pointers without refcountsLinus Torvalds2024-02-012-177/+78
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The eventfs inode had pointers to dentries (and child dentries) without actually holding a refcount on said pointer. That is fundamentally broken, and while eventfs tried to then maintain coherence with dentries going away by hooking into the '.d_iput' callback, that doesn't actually work since it's not ordered wrt lookups. There were two reasonms why eventfs tried to keep a pointer to a dentry: - the creation of a 'events' directory would actually have a stable dentry pointer that it created with tracefs_start_creating(). And it needed that dentry when tearing it all down again in eventfs_remove_events_dir(). This use is actually ok, because the special top-level events directory dentries are actually stable, not just a temporary cache of the eventfs data structures. - the 'eventfs_inode' (aka ei) needs to stay around as long as there are dentries that refer to it. It then used these dentry pointers as a replacement for doing reference counting: it would try to make sure that there was only ever one dentry associated with an event_inode, and keep a child dentry array around to see which dentries might still refer to the parent ei. This gets rid of the invalid dentry pointer use, and renames the one valid case to a different name to make it clear that it's not just any random dentry. The magic child dentry array that is kind of a "reverse reference list" is simply replaced by having child dentries take a ref to the ei. As does the directory dentries. That makes the broken use case go away. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131185513.280463000@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Clean up dentry ops and add revalidate functionLinus Torvalds2024-02-013-13/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In order for the dentries to stay up-to-date with the eventfs changes, just add a 'd_revalidate' function that checks the 'is_freed' bit. Also, clean up the dentry release to actually use d_release() rather than the slightly odd d_iput() function. We don't care about the inode, all we want to do is to get rid of the refcount to the eventfs data added by dentry->d_fsdata. It would probably be cleaner to make eventfs its own filesystem, or at least set its own dentry ops when looking up eventfs files. But as it is, only eventfs dentries use d_fsdata, so we don't really need to split these things up by use. Another thing that might be worth doing is to make all eventfs lookups mark their dentries as not worth caching. We could do that with d_delete(), but the DCACHE_DONTCACHE flag would likely be even better. As it is, the dentries are all freeable, but they only tend to get freed at memory pressure rather than more proactively. But that's a separate issue. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131185513.124644253@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Remove unused d_parent pointer fieldLinus Torvalds2024-02-012-5/+1
| | | | | | | | | | | | | | | | | | | It's never used Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.961772428@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: dentry lookup crapectomyLinus Torvalds2024-02-013-297/+50
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The dentry lookup for eventfs files was very broken, and had lots of signs of the old situation where the filesystem names were all created statically in the dentry tree, rather than being looked up dynamically based on the eventfs data structures. You could see it in the naming - how it claimed to "create" dentries rather than just look up the dentries that were given it. You could see it in various nonsensical and very incorrect operations, like using "simple_lookup()" on the dentries that were passed in, which only results in those dentries becoming negative dentries. Which meant that any other lookup would possibly return ENOENT if it saw that negative dentry before the data was then later filled in. You could see it in the immense amount of nonsensical code that didn't actually just do lookups. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131233227.73db55e1@gandalf.local.home Cc: stable@vger.kernel.org Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Mark Rutland <mark.rutland@arm.com> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: Avoid using the ei->dentry pointer unnecessarilyLinus Torvalds2024-01-311-14/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The eventfs_find_events() code tries to walk up the tree to find the event directory that a dentry belongs to, in order to then find the eventfs inode that is associated with that event directory. However, it uses an odd combination of walking the dentry parent, looking up the eventfs inode associated with that, and then looking up the dentry from there. Repeat. But the code shouldn't have back-pointers to dentries in the first place, and it should just walk the dentry parenthood chain directly. Similarly, 'set_top_events_ownership()' looks up the dentry from the eventfs inode, but the only reason it wants a dentry is to look up the superblock in order to look up the root dentry. But it already has the real filesystem inode, which has that same superblock pointer. So just pass in the superblock pointer using the information that's already there, instead of looking up extraneous data that is irrelevant. Link: https://lore.kernel.org/linux-trace-kernel/202401291043.e62e89dc-oliver.sang@intel.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.638645365@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Initialize the tracefs inode properlyLinus Torvalds2024-01-311-4/+2
| | | | | | | | | | | | | | | | | | | | | | | The tracefs-specific fields in the inode were not initialized before the inode was exposed to others through the dentry with 'd_instantiate()'. Move the field initializations up to before the d_instantiate. Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.478449628@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: Zero out the tracefs_inode when allocating itSteven Rostedt (Google)2024-01-312-3/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | eventfs uses the tracefs_inode and assumes that it's already initialized to zero. That is, it doesn't set fields to zero (like ti->private) after getting its tracefs_inode. This causes bugs due to stale values. Just initialize the entire structure to zero on allocation so there isn't any more surprises. This is a partial fix to access to ti->private. The assignment still needs to be made before the dentry is instantiated. Link: https://lore.kernel.org/linux-trace-kernel/20240131185512.315825944@goodmis.org Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: 5790b1fb3d672 ("eventfs: Remove eventfs_file and just use eventfs_inode") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202401291043.e62e89dc-oliver.sang@intel.com Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: remove stale 'update_gid' codeLinus Torvalds2024-01-282-39/+0
| | | | | | | | | | | The 'eventfs_update_gid()' function is no longer called, so remove it (and the helper function it uses). Link: https://lore.kernel.org/all/CAHk-=wj+DsZZ=2iTUkJ-Nojs9fjYMvPs1NuoM3yK7aTDtJfPYQ@mail.gmail.com/ Fixes: 8186fff7ab64 ("tracefs/eventfs: Use root and instance inodes as default ownership") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Save directory inodes in the eventfs_inode structureSteven Rostedt (Google)2024-01-232-6/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The eventfs inodes and directories are allocated when referenced. But this leaves the issue of keeping consistent inode numbers and the number is only saved in the inode structure itself. When the inode is no longer referenced, it can be freed. When the file that the inode was representing is referenced again, the inode is once again created, but the inode number needs to be the same as it was before. Just making the inode numbers the same for all files is fine, but that does not work with directories. The find command will check for loops via the inode number and having the same inode number for directories triggers: # find /sys/kernel/tracing find: File system loop detected; '/sys/kernel/debug/tracing/events/initcall/initcall_finish' is part of the same file system loop as '/sys/kernel/debug/tracing/events/initcall'. [..] Linus pointed out that the eventfs_inode structure ends with a single 32bit int, and on 64 bit machines, there's likely a 4 byte hole due to alignment. We can use this hole to store the inode number for the eventfs_inode. All directories in eventfs are represented by an eventfs_inode and that data structure can hold its inode number. That last int was also purposely placed at the end of the structure to prevent holes from within. Now that there's a 4 byte number to hold the inode, both the inode number and the last integer can be moved up in the structure for better cache locality, where the llist and rcu fields can be moved to the end as they are only used when the eventfs_inode is being deleted. Link: https://lore.kernel.org/all/CAMuHMdXKiorg-jiuKoZpfZyDJ3Ynrfb8=X+c7x0Eewxn-YRdCA@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240122152748.46897388@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Fixes: 53c41052ba31 ("eventfs: Have the inodes all for files and directories all be the same") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Reviewed-by: Kees Cook <keescook@chromium.org>
* eventfs: Use kcalloc() instead of kzalloc()Erick Archer2024-01-161-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | As noted in the "Deprecated Interfaces, Language Features, Attributes, and Conventions" documentation [1], size calculations (especially multiplication) should not be performed in memory allocator (or similar) function arguments due to the risk of them overflowing. This could lead to values wrapping around and a smaller allocation being made than the caller was expecting. Using those allocations could lead to linear overflows of heap memory and other misbehaviors. So, use the purpose specific kcalloc() function instead of the argument size * count in the kzalloc() function. [1] https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments Link: https://lore.kernel.org/linux-trace-kernel/20240115181658.4562-1-erick.archer@gmx.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mark Rutland <mark.rutland@arm.com> Link: https://github.com/KSPP/linux/issues/162 Signed-off-by: Erick Archer <erick.archer@gmx.com> Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Do not create dentries nor inodes in iterate_sharedSteven Rostedt (Google)2024-01-161-15/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The original eventfs code added a wrapper around the dcache_readdir open callback and created all the dentries and inodes at open, and increment their ref count. A wrapper was added around the dcache_readdir release function to decrement all the ref counts of those created inodes and dentries. But this proved to be buggy[1] for when a kprobe was created during a dir read, it would create a dentry between the open and the release, and because the release would decrement all ref counts of all files and directories, that would include the kprobe directory that was not there to have its ref count incremented in open. This would cause the ref count to go to negative and later crash the kernel. To solve this, the dentries and inodes that were created and had their ref count upped in open needed to be saved. That list needed to be passed from the open to the release, so that the release would only decrement the ref counts of the entries that were incremented in the open. Unfortunately, the dcache_readdir logic was already using the file->private_data, which is the only field that can be used to pass information from the open to the release. What was done was the eventfs created another descriptor that had a void pointer to save the dcache_readdir pointer, and it wrapped all the callbacks, so that it could save the list of entries that had their ref counts incremented in the open, and pass it to the release. The wrapped callbacks would just put back the dcache_readdir pointer and call the functions it used so it could still use its data[2]. But Linus had an issue with the "hijacking" of the file->private_data (unfortunately this discussion was on a security list, so no public link). Which we finally agreed on doing everything within the iterate_shared callback and leave the dcache_readdir out of it[3]. All the information needed for the getents() could be created then. But this ended up being buggy too[4]. The iterate_shared callback was not the right place to create the dentries and inodes. Even Christian Brauner had issues with that[5]. An attempt was to go back to creating the inodes and dentries at the open, create an array to store the information in the file->private_data, and pass that information to the other callbacks.[6] The difference between that and the original method, is that it does not use dcache_readdir. It also does not up the ref counts of the dentries and pass them. Instead, it creates an array of a structure that saves the dentry's name and inode number. That information is used in the iterate_shared callback, and the array is freed in the dir release. The dentries and inodes created in the open are not used for the iterate_share or release callbacks. Just their names and inode numbers. Linus did not like that either[7] and just wanted to remove the dentries being created in iterate_shared and use the hard coded inode numbers. [ All this while Linus enjoyed an unexpected vacation during the merge window due to lack of power. ] [1] https://lore.kernel.org/linux-trace-kernel/20230919211804.230edf1e@gandalf.local.home/ [2] https://lore.kernel.org/linux-trace-kernel/20230922163446.1431d4fa@gandalf.local.home/ [3] https://lore.kernel.org/linux-trace-kernel/20240104015435.682218477@goodmis.org/ [4] https://lore.kernel.org/all/202401152142.bfc28861-oliver.sang@intel.com/ [5] https://lore.kernel.org/all/20240111-unzahl-gefegt-433acb8a841d@brauner/ [6] https://lore.kernel.org/all/20240116114711.7e8637be@gandalf.local.home/ [7] https://lore.kernel.org/all/20240116170154.5bf0a250@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240116211353.573784051@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Fixes: 493ec81a8fb8 ("eventfs: Stop using dcache_readdir() for getdents()") Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202401152142.bfc28861-oliver.sang@intel.com Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Have the inodes all for files and directories all be the sameSteven Rostedt (Google)2024-01-161-0/+10
| | | | | | | | | | | | | | | | | | | | | | The dentries and inodes are created in the readdir for the sole purpose of getting a consistent inode number. Linus stated that is unnecessary, and that all inodes can have the same inode number. For a virtual file system they are pretty meaningless. Instead use a single unique inode number for all files and one for all directories. Link: https://lore.kernel.org/all/20240116133753.2808d45e@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240116211353.412180363@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Christian Brauner <brauner@kernel.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Ajay Kaher <ajay.kaher@broadcom.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Shortcut eventfs_iterate() by skipping entries already readSteven Rostedt (Google)2024-01-041-13/+10
| | | | | | | | | | | | | | | | | | | | | | As the ei->entries array is fixed for the duration of the eventfs_inode, it can be used to skip over already read entries in eventfs_iterate(). That is, if ctx->pos is greater than zero, there's no reason in doing the loop across the ei->entries array for the entries less than ctx->pos. Instead, start the lookup of the entries at the current ctx->pos. Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.494956957@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Read ei->entries before ei->children in eventfs_iterate()Steven Rostedt (Google)2024-01-041-23/+23
| | | | | | | | | | | | | | | | | | | | In order to apply a shortcut to skip over the current ctx->pos immediately, by using the ei->entries array, the reading of that array should be first. Moving the array reading before the linked list reading will make the shortcut change diff nicer to read. Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.333115095@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Do ctx->pos update for all iterations in eventfs_iterate()Steven Rostedt (Google)2024-01-041-7/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The ctx->pos was only updated when it added an entry, but the "skip to current pos" check (c--) happened for every loop regardless of if the entry was added or not. This inconsistency caused readdir to be incorrect. It was due to: for (i = 0; i < ei->nr_entries; i++) { if (c > 0) { c--; continue; } mutex_lock(&eventfs_mutex); /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); goto out; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); [..] ctx->pos++; } But this can cause the iterator to return a file that was already read. That's because of the way the callback() works. Some events may not have all files, and the callback can return 0 to tell eventfs to skip the file for this directory. for instance, we have: # ls /sys/kernel/tracing/events/ftrace/function format hist hist_debug id inject and # ls /sys/kernel/tracing/events/sched/sched_switch/ enable filter format hist hist_debug id inject trigger Where the function directory is missing "enable", "filter" and "trigger". That's because the callback() for events has: static int event_callback(const char *name, umode_t *mode, void **data, const struct file_operations **fops) { struct trace_event_file *file = *data; struct trace_event_call *call = file->event_call; [..] /* * Only event directories that can be enabled should have * triggers or filters, with the exception of the "print" * event that can have a "trigger" file. */ if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) { if (call->class->reg && strcmp(name, "enable") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_enable_fops; return 1; } if (strcmp(name, "filter") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_event_filter_fops; return 1; } } if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) || strcmp(trace_event_name(call), "print") == 0) { if (strcmp(name, "trigger") == 0) { *mode = TRACE_MODE_WRITE; *fops = &event_trigger_fops; return 1; } } [..] return 0; } Where the function event has the TRACE_EVENT_FL_IGNORE_ENABLE set. This means that the entries array elements for "enable", "filter" and "trigger" when called on the function event will have the callback return 0 and not 1, to tell eventfs to skip these files for it. Because the "skip to current ctx->pos" check happened for all entries, but the ctx->pos++ only happened to entries that exist, it would confuse the reading of a directory. Which would cause: # ls /sys/kernel/tracing/events/ftrace/function/ format hist hist hist_debug hist_debug id inject inject The missing "enable", "filter" and "trigger" caused ls to show "hist", "hist_debug" and "inject" twice. Update the ctx->pos for every iteration to keep its update and the "skip" update consistent. This also means that on error, the ctx->pos needs to be decremented if it was incremented without adding something. Link: https://lore.kernel.org/all/20240104150500.38b15a62@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.172295263@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fixes: 493ec81a8fb8e ("eventfs: Stop using dcache_readdir() for getdents()") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Have eventfs_iterate() stop immediately if ei->is_freed is setSteven Rostedt (Google)2024-01-041-5/+6
| | | | | | | | | | | | | | | | | | | If ei->is_freed is set in eventfs_iterate(), it means that the directory that is being iterated on is in the process of being freed. Just exit the loop immediately when that is ever detected, and separate out the return of the entry->callback() from ei->is_freed. Link: https://lore.kernel.org/linux-trace-kernel/20240104220048.016261289@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs/eventfs: Use root and instance inodes as default ownershipSteven Rostedt (Google)2024-01-043-90/+190
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Instead of walking the dentries on mount/remount to update the gid values of all the dentries if a gid option is specified on mount, just update the root inode. Add .getattr, .setattr, and .permissions on the tracefs inode operations to update the permissions of the files and directories. For all files and directories in the top level instance: /sys/kernel/tracing/* It will use the root inode as the default permissions. The inode that represents: /sys/kernel/tracing (or wherever it is mounted). When an instance is created: mkdir /sys/kernel/tracing/instance/foo The directory "foo" and all its files and directories underneath will use the default of what foo is when it was created. A remount of tracefs will not affect it. If a user were to modify the permissions of any file or directory in tracefs, it will also no longer be modified by a change in ownership of a remount. The events directory, if it is in the top level instance, will use the tracefs root inode as the default ownership for itself and all the files and directories below it. For the events directory in an instance ("foo"), it will keep the ownership of what it was when it was created, and that will be used as the default ownership for the files and directories beneath it. Link: https://lore.kernel.org/linux-trace-kernel/CAHk-=wjVdGkjDXBbvLn2wbZnqP4UsH46E3gqJ9m7UG6DpX2+WA@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20240103215016.1e0c9811@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Stop using dcache_readdir() for getdents()Steven Rostedt (Google)2024-01-041-130/+64
| | | | | | | | | | | | | | | | | | | | | | The eventfs creates dynamically allocated dentries and inodes. Using the dcache_readdir() logic for its own directory lookups requires hiding the cursor of the dcache logic and playing games to allow the dcache_readdir() to still have access to the cursor while the eventfs saved what it created and what it needs to release. Instead, just have eventfs have its own iterate_shared callback function that will fill in the dent entries. This simplifies the code quite a bit. Link: https://lore.kernel.org/linux-trace-kernel/20240104015435.682218477@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ajay Kaher <akaher@vmware.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Remove "lookup" parameter from create_dir/file_dentry()Steven Rostedt (Google)2024-01-041-35/+20
| | | | | | | | | | | | | | | | | | | | | The "lookup" parameter is a way to differentiate the call to create_file/dir_dentry() from when it's just a lookup (no need to up the dentry refcount) and accessed via a readdir (need to up the refcount). But reality, it just makes the code more complex. Just up the refcount and let the caller decide to dput() the result or not. Link: https://lore.kernel.org/linux-trace-kernel/20240103102553.17a19cea@gandalf.local.home Link: https://lore.kernel.org/linux-trace-kernel/20240104015435.517502710@goodmis.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Ajay Kaher <akaher@vmware.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Fix bitwise fields for "is_events"Steven Rostedt (Google)2024-01-021-1/+1
| | | | | | | | | | | | | | | | A flag was needed to denote which eventfs_inode was the "events" directory, so a bit was taken from the "nr_entries" field, as there's not that many entries, and 2^30 is plenty. But the bit number for nr_entries was not updated to reflect the bit taken from it, which would add an unnecessary integer to the structure. Link: https://lore.kernel.org/linux-trace-kernel/20240102151832.7ca87275@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 7e8358edf503e ("eventfs: Fix file and directory uid and gid ownership") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* tracefs: Check for dentry->d_inode exists in set_gid()Steven Rostedt (Google)2024-01-021-0/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a getdents() is called on the tracefs directory but does not get all the files, it can leave a "cursor" dentry in the d_subdirs list of tracefs dentry. This cursor dentry does not have a d_inode for it. Before referencing tracefs_inode from the dentry, the d_inode must first be checked if it has content. If not, then it's not a tracefs_inode and can be ignored. The following caused a crash: #define getdents64(fd, dirp, count) syscall(SYS_getdents64, fd, dirp, count) #define BUF_SIZE 256 #define TDIR "/tmp/file0" int main(void) { char buf[BUF_SIZE]; int fd; int n; mkdir(TDIR, 0777); mount(NULL, TDIR, "tracefs", 0, NULL); fd = openat(AT_FDCWD, TDIR, O_RDONLY); n = getdents64(fd, buf, BUF_SIZE); ret = mount(NULL, TDIR, NULL, MS_NOSUID|MS_REMOUNT|MS_RELATIME|MS_LAZYTIME, "gid=1000"); return 0; } That's because the 256 BUF_SIZE was not big enough to read all the dentries of the tracefs file system and it left a "cursor" dentry in the subdirs of the tracefs root inode. Then on remounting with "gid=1000", it would cause an iteration of all dentries which hit: ti = get_tracefs(dentry->d_inode); if (ti && (ti->flags & TRACEFS_EVENT_INODE)) eventfs_update_gid(dentry, gid); Which crashed because of the dereference of the cursor dentry which had a NULL d_inode. In the subdir loop of the dentry lookup of set_gid(), if a child has a NULL d_inode, simply skip it. Link: https://lore.kernel.org/all/20240102135637.3a21fb10@gandalf.local.home/ Link: https://lore.kernel.org/linux-trace-kernel/20240102151249.05da244d@gandalf.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 7e8358edf503e ("eventfs: Fix file and directory uid and gid ownership") Reported-by: "Ubisectech Sirius" <bugreport@ubisectech.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Fix file and directory uid and gid ownershipSteven Rostedt (Google)2023-12-223-10/+103
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It was reported that when mounting the tracefs file system with a gid other than root, the ownership did not carry down to the eventfs directory due to the dynamic nature of it. A fix was done to solve this, but it had two issues. (a) if the attr passed into update_inode_attr() was NULL, it didn't do anything. This is true for files that have not had a chown or chgrp done to itself or any of its sibling files, as the attr is allocated for all children when any one needs it. # umount /sys/kernel/tracing # mount -o rw,seclabel,relatime,gid=1000 -t tracefs nodev /mnt # ls -ld /mnt/events/sched drwxr-xr-x 28 root rostedt 0 Dec 21 13:12 /mnt/events/sched/ # ls -ld /mnt/events/sched/sched_switch drwxr-xr-x 2 root rostedt 0 Dec 21 13:12 /mnt/events/sched/sched_switch/ But when checking the files: # ls -l /mnt/events/sched/sched_switch total 0 -rw-r----- 1 root root 0 Dec 21 13:12 enable -rw-r----- 1 root root 0 Dec 21 13:12 filter -r--r----- 1 root root 0 Dec 21 13:12 format -r--r----- 1 root root 0 Dec 21 13:12 hist -r--r----- 1 root root 0 Dec 21 13:12 id -rw-r----- 1 root root 0 Dec 21 13:12 trigger (b) When the attr does not denote the UID or GID, it defaulted to using the parent uid or gid. This is incorrect as changing the parent uid or gid will automatically change all its children. # chgrp tracing /mnt/events/timer # ls -ld /mnt/events/timer drwxr-xr-x 2 root tracing 0 Dec 21 14:34 /mnt/events/timer # ls -l /mnt/events/timer total 0 -rw-r----- 1 root root 0 Dec 21 14:35 enable -rw-r----- 1 root root 0 Dec 21 14:35 filter drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 hrtimer_start drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_expire drwxr-xr-x 2 root tracing 0 Dec 21 14:35 itimer_state drwxr-xr-x 2 root tracing 0 Dec 21 14:35 tick_stop drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_cancel drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_entry drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_expire_exit drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_init drwxr-xr-x 2 root tracing 0 Dec 21 14:35 timer_start At first it was thought that this could be easily fixed by just making the default ownership of the superblock when it was mounted. But this does not handle the case of: # chgrp tracing instances # mkdir instances/foo If the superblock was used, then the group ownership would be that of what it was when it was mounted, when it should instead be "tracing". Instead, set a flag for the top level eventfs directory ("events") to flag which eventfs_inode belongs to it. Since the "events" directory's dentry and inode are never freed, it does not need to use its attr field to restore its mode and ownership. Use the this eventfs_inode's attr as the default ownership for all the files and directories underneath it. When the events eventfs_inode is created, it sets its ownership to its parent uid and gid. As the events directory is created at boot up before it gets mounted, this will always be uid=0 and gid=0. If it's created via an instance, then it will take the ownership of the instance directory. When the file system is mounted, it will update all the gids if one is specified. This will have a callback to update the events evenfs_inode's default entries. When a file or directory is created under the events directory, it will walk the ei->dentry parents until it finds the evenfs_inode that belongs to the events directory to retrieve the default uid and gid values. Link: https://lore.kernel.org/all/CAHk-=wiwQtUHvzwyZucDq8=Gtw+AnwScyLhpFswrQ84PjhoGsg@mail.gmail.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231221190757.7eddbca9@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Dongliang Cui <cuidongliang390@gmail.com> Cc: Hongyu Jin <hongyu.jin@unisoc.com> Fixes: 0dfc852b6fe3 ("eventfs: Have event files and directories default to parent uid and gid") Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Tested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
* eventfs: Have event files and directories default to parent uid and gidSteven Rostedt (Google)2023-12-211-3/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Dongliang reported: I found that in the latest version, the nodes of tracefs have been changed to dynamically created. This has caused me to encounter a problem where the gid I specified in the mounting parameters cannot apply to all files, as in the following situation: /data/tmp/events # mount | grep tracefs tracefs on /data/tmp type tracefs (rw,seclabel,relatime,gid=3012) gid 3012 = readtracefs /data/tmp # ls -lh total 0 -r--r----- 1 root readtracefs 0 1970-01-01 08:00 README -r--r----- 1 root readtracefs 0 1970-01-01 08:00 available_events ums9621_1h10:/data/tmp/events # ls -lh total 0 drwxr-xr-x 2 root root 0 2023-12-19 00:56 alarmtimer drwxr-xr-x 2 root root 0 2023-12-19 00:56 asoc It will prevent certain applications from accessing tracefs properly, I try to avoid this issue by making the following modifications. To fix this, have the files created default to taking the ownership of the parent dentry unless the ownership was previously set by the user. Link: https://lore.kernel.org/linux-trace-kernel/1703063706-30539-1-git-send-email-dongliang.cui@unisoc.com/ Link: https://lore.kernel.org/linux-trace-kernel/20231220105017.1489d790@gandalf.local.home Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Hongyu Jin <hongyu.jin@unisoc.com> Fixes: 28e12c09f5aa0 ("eventfs: Save ownership and mode") Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reported-by: Dongliang Cui <cuidongliang390@gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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