Messages in this thread Patch in this message | | | Date | Fri, 07 Aug 2009 14:45:18 -0700 | From | Darren Hart <> | Subject | [PATCH] futex: Fix handling of bad requeue syscall pairing |
| |
From: Darren Hart <dvhltc@us.ibm.com>
If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call other than futex_wait_requeue_pi(), the q.rt_waiter will 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 mis-pairing in futex_requeue(), bail out, sending -EINVAL to user-space.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Ingo Molnar <mingo@elte.hu> CC: Eric Dumazet <eric.dumazet@gmail.com> CC: John Kacur <jkacur@redhat.com> CC: Dinakar Guniguntala <dino@in.ibm.com> CC: John Stultz <johnstul@us.ibm.com> ---
kernel/futex.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c index 578c7b7..d806d6c 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1306,8 +1306,15 @@ 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 -- Darren Hart IBM Linux Technology Center Real-Time Linux Team
| |