Messages in this thread Patch in this message | | | Date | Mon, 10 Aug 2009 18:42:34 GMT | From | tip-bot for Darren Hart <> | Subject | [tip:core/urgent] futex: Fix handling of bad requeue syscall pairing |
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Commit-ID: 392741e0a4e17c82e3978b7fcbf04291294dc0a1 Gitweb: http://git.kernel.org/tip/392741e0a4e17c82e3978b7fcbf04291294dc0a1 Author: Darren Hart <dvhltc@us.ibm.com> AuthorDate: Fri, 7 Aug 2009 15:20:48 -0700 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Mon, 10 Aug 2009 20:38:11 +0200
futex: Fix handling of bad requeue syscall pairing
If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call other the futex_wait_requeue_pi(), the q.rt_waiter may be null. If so, this will result in an oops from the following call graph:
futex_requeue() rt_mutex_start_proxy_lock() task_blocks_on_rt_mutex() waiter->task dereference OOPS
We currently WARN_ON() if this is detected, clearly this is inadequate. If we detect a mispairing in futex_requeue(), bail out, seding -EINVAL to user-space.
V2: Fix parenthesis warnings.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: John Kacur <jkacur@redhat.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Dinakar Guniguntala <dino@in.ibm.com> Cc: John Stultz <johnstul@linux.vnet.ibm.com> LKML-Reference: <4A7CA8C0.7010809@us.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- kernel/futex.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c index 8cc3ee1..e18cfbd 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1256,8 +1256,15 @@ retry_private: if (!match_futex(&this->key, &key1)) continue; - WARN_ON(!requeue_pi && this->rt_waiter); - WARN_ON(requeue_pi && !this->rt_waiter); + /* + * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always + * be paired with each other and no other futex ops. + */ + if ((requeue_pi && !this->rt_waiter) || + (!requeue_pi && this->rt_waiter)) { + ret = -EINVAL; + break; + } /* * Wake nr_wake waiters. For requeue_pi, if we acquired the
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