Skip to content
Commit 3245d6ac authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

exit: fix race between wait_consider_task() and wait_task_zombie()



wait_consider_task() checks EXIT_ZOMBIE after EXIT_DEAD/EXIT_TRACE and
both checks can fail if we race with EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE
change in between, gcc needs to reload p->exit_state after
security_task_wait().  In this case ->notask_error will be wrongly
cleared and do_wait() can hang forever if it was the last eligible
child.

Many thanks to Arne who carefully investigated the problem.

Note: this bug is very old but it was pure theoretical until commit
b3ab0316 ("wait: completely ignore the EXIT_DEAD tasks").  Before
this commit "-O2" was probably enough to guarantee that compiler won't
read ->exit_state twice.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reported-by: default avatarArne Goedeke <el@laramies.com>
Tested-by: default avatarArne Goedeke <el@laramies.com>
Cc: <stable@vger.kernel.org>	[3.15+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent eb4f73b4
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment