fs/aio: Add explicit RCU grace period when freeing kioctx

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commit a6d7cff472 upstream.

While fixing refcounting, e34ecee2ae ("aio: Fix a trinity splat")
incorrectly removed explicit RCU grace period before freeing kioctx.
The intention seems to be depending on the internal RCU grace periods
of percpu_ref; however, percpu_ref uses a different flavor of RCU,
sched-RCU.  This can lead to kioctx being freed while RCU read
protected dereferences are still in progress.

Fix it by updating free_ioctx() to go through call_rcu() explicitly.

v2: Comment added to explain double bouncing.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Jann Horn <jannh@google.com>
Fixes: e34ecee2ae ("aio: Fix a trinity splat")
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

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Tejun Heo 2018-03-14 12:10:17 -07:00 • committed by Ben Hutchings

parent 147c00b31d

commit 178eb82398

1 changed files with 19 additions and 4 deletions

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fs/aio.c

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