diff options
author | Brian Norris <briannorris@chromium.org> | 2022-08-27 02:44:17 +0200 |
---|---|---|
committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-09-08 23:10:54 +0200 |
commit | 47311db8e8f33011d90dee76b39c8886120cdda4 (patch) | |
tree | 29eecd63fe2aa6f88e5bf74d3db5f817482f91f7 /fs/tracefs/inode.c | |
parent | kprobes: Prohibit probes in gate area (diff) | |
download | linux-47311db8e8f33011d90dee76b39c8886120cdda4.tar.xz linux-47311db8e8f33011d90dee76b39c8886120cdda4.zip |
tracefs: Only clobber mode/uid/gid on remount if asked
Users may have explicitly configured their tracefs permissions; we
shouldn't overwrite those just because a second mount appeared.
Only clobber if the options were provided at mount time.
Note: the previous behavior was especially surprising in the presence of
automounted /sys/kernel/debug/tracing/.
Existing behavior:
## Pre-existing status: tracefs is 0755.
# stat -c '%A' /sys/kernel/tracing/
drwxr-xr-x
## (Re)trigger the automount.
# umount /sys/kernel/debug/tracing
# stat -c '%A' /sys/kernel/debug/tracing/.
drwx------
## Unexpected: the automount changed mode for other mount instances.
# stat -c '%A' /sys/kernel/tracing/
drwx------
New behavior (after this change):
## Pre-existing status: tracefs is 0755.
# stat -c '%A' /sys/kernel/tracing/
drwxr-xr-x
## (Re)trigger the automount.
# umount /sys/kernel/debug/tracing
# stat -c '%A' /sys/kernel/debug/tracing/.
drwxr-xr-x
## Expected: the automount does not change other mount instances.
# stat -c '%A' /sys/kernel/tracing/
drwxr-xr-x
Link: https://lkml.kernel.org/r/20220826174353.2.Iab6e5ea57963d6deca5311b27fb7226790d44406@changeid
Cc: stable@vger.kernel.org
Fixes: 4282d60689d4f ("tracefs: Add new tracefs file system")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'fs/tracefs/inode.c')
-rw-r--r-- | fs/tracefs/inode.c | 31 |
1 files changed, 23 insertions, 8 deletions
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c index 81d26abf486f..da85b3979195 100644 --- a/fs/tracefs/inode.c +++ b/fs/tracefs/inode.c @@ -141,6 +141,8 @@ struct tracefs_mount_opts { kuid_t uid; kgid_t gid; umode_t mode; + /* Opt_* bitfield. */ + unsigned int opts; }; enum { @@ -241,6 +243,7 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts) kgid_t gid; char *p; + opts->opts = 0; opts->mode = TRACEFS_DEFAULT_MODE; while ((p = strsep(&data, ",")) != NULL) { @@ -275,24 +278,36 @@ static int tracefs_parse_options(char *data, struct tracefs_mount_opts *opts) * but traditionally tracefs has ignored all mount options */ } + + opts->opts |= BIT(token); } return 0; } -static int tracefs_apply_options(struct super_block *sb) +static int tracefs_apply_options(struct super_block *sb, bool remount) { struct tracefs_fs_info *fsi = sb->s_fs_info; struct inode *inode = d_inode(sb->s_root); struct tracefs_mount_opts *opts = &fsi->mount_opts; - inode->i_mode &= ~S_IALLUGO; - inode->i_mode |= opts->mode; + /* + * On remount, only reset mode/uid/gid if they were provided as mount + * options. + */ + + if (!remount || opts->opts & BIT(Opt_mode)) { + inode->i_mode &= ~S_IALLUGO; + inode->i_mode |= opts->mode; + } - inode->i_uid = opts->uid; + if (!remount || opts->opts & BIT(Opt_uid)) + inode->i_uid = opts->uid; - /* Set all the group ids to the mount option */ - set_gid(sb->s_root, opts->gid); + if (!remount || opts->opts & BIT(Opt_gid)) { + /* Set all the group ids to the mount option */ + set_gid(sb->s_root, opts->gid); + } return 0; } @@ -307,7 +322,7 @@ static int tracefs_remount(struct super_block *sb, int *flags, char *data) if (err) goto fail; - tracefs_apply_options(sb); + tracefs_apply_options(sb, true); fail: return err; @@ -359,7 +374,7 @@ static int trace_fill_super(struct super_block *sb, void *data, int silent) sb->s_op = &tracefs_super_operations; - tracefs_apply_options(sb); + tracefs_apply_options(sb, false); return 0; |