summaryrefslogtreecommitdiffstats
path: root/ipc/ipc_sysctl.c
diff options
context:
space:
mode:
authorManfred Spraul <manfred@colorfullife.com>2019-05-15 00:46:33 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-15 04:52:52 +0200
commit3278a2c20cb302d27e6f6ee45a3f57361176e426 (patch)
tree94ce43abadc5a660dda63662a28c7000e92154d4 /ipc/ipc_sysctl.c
parentipc: allow boot time extension of IPCMNI from 32k to 16M (diff)
downloadlinux-3278a2c20cb302d27e6f6ee45a3f57361176e426.tar.xz
linux-3278a2c20cb302d27e6f6ee45a3f57361176e426.zip
ipc: conserve sequence numbers in ipcmni_extend mode
Rewrite, based on the patch from Waiman Long: The mixing in of a sequence number into the IPC IDs is probably to avoid ID reuse in userspace as much as possible. With ipcmni_extend mode, the number of usable sequence numbers is greatly reduced leading to higher chance of ID reuse. To address this issue, we need to conserve the sequence number space as much as possible. Right now, the sequence number is incremented for every new ID created. In reality, we only need to increment the sequence number when new allocated ID is not greater than the last one allocated. It is in such case that the new ID may collide with an existing one. This is being done irrespective of the ipcmni mode. In order to avoid any races, the index is first allocated and then the pointer is replaced. Changes compared to the initial patch: - Handle failures from idr_alloc(). - Avoid that concurrent operations can see the wrong sequence number. (This is achieved by using idr_replace()). - IPCMNI_SEQ_SHIFT is not a constant, thus renamed to ipcmni_seq_shift(). - IPCMNI_SEQ_MAX is not a constant, thus renamed to ipcmni_seq_max(). Link: http://lkml.kernel.org/r/20190329204930.21620-2-longman@redhat.com Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Signed-off-by: Waiman Long <longman@redhat.com> Suggested-by: Matthew Wilcox <willy@infradead.org> Acked-by: Waiman Long <longman@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: "Eric W . Biederman" <ebiederm@xmission.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Kees Cook <keescook@chromium.org> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org> Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/ipc_sysctl.c')
0 files changed, 0 insertions, 0 deletions