ipc/util.c: correct comment in ipc_obtain_object_check

manfred-colorfu · torvalds · commit 2e5ceb452c9b · 2018-08-22T10:52:52.000-07:00
The comment that explains ipc_obtain_object_check is wrong: The function checks the sequence number, not the reference counter. Note that checking the reference counter would be meaningless: The reference counter is decreased without holding any locks, thus an object with kern_ipc_perm.deleted=true may disappear at the end of the next rcu grace period. Link: http://lkml.kernel.org/r/20180712185241.4017-6-manfred@colorfullife.com Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Reviewed-by: Davidlohr Bueso <dbueso@suse.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Kees Cook <keescook@chromium.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/util.c b/ipc/util.c
@@ -629,8 +629,8 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
  * @ids: ipc identifier set
  * @id: ipc id to look for
  *
- * Similar to ipc_obtain_object_idr() but also checks
- * the ipc object reference counter.
+ * Similar to ipc_obtain_object_idr() but also checks the ipc object
+ * sequence number.
  *
  * Call inside the RCU critical section.
  * The ipc object is *not* locked on exit.

Original file line number	Diff line number	Diff line change
`@@ -629,8 +629,8 @@ struct kern_ipc_perm ipc_lock(struct ipc_ids ids, int id)`
`629`	`629`	`* @ids: ipc identifier set`
`630`	`630`	`* @id: ipc id to look for`
`631`	`631`	`*`
`632`		`- * Similar to ipc_obtain_object_idr() but also checks`
`633`		`- * the ipc object reference counter.`
	`632`	`+ * Similar to ipc_obtain_object_idr() but also checks the ipc object`
	`633`	`+ * sequence number.`
`634`	`634`	`*`
`635`	`635`	`* Call inside the RCU critical section.`
`636`	`636`	`* The ipc object is not locked on exit.`