| From | lizf@kernel ... | Subject | [PATCH 3.4 36/91] futex: Unlock hb->lock in futex_wait_requeue_pi() error path | Date | Thu, 27 Nov 2014 16:42:19 +0800 |
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From: Thomas Gleixner <tglx@linutronix.de>
3.4.105-rc1 review patch. If anyone has any objections, please let me know.
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commit 13c42c2f43b19aab3195f2d357db00d1e885eaa8 upstream.
futex_wait_requeue_pi() calls futex_wait_setup(). If futex_wait_setup() succeeds it returns with hb->lock held and preemption disabled. Now the sanity check after this does:
if (match_futex(&q.key, &key2)) { ret = -EINVAL; goto out_put_keys; }
which releases the keys but does not release hb->lock.
So we happily return to user space with hb->lock held and therefor preemption disabled.
Unlock hb->lock before taking the exit route.
Reported-by: Dave "Trinity" Jones <davej@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Darren Hart <dvhart@linux.intel.com> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de> [lizf: Backported to 3.4: queue_unlock() takes two parameters] Signed-off-by: Zefan Li <lizefan@huawei.com> --- kernel/futex.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/futex.c b/kernel/futex.c index 9396b7b..41dfb18 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2460,6 +2460,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, * shared futexes. We need to compare the keys: */ if (match_futex(&q.key, &key2)) { + queue_unlock(&q, hb); ret = -EINVAL; goto out_put_keys; } -- 1.9.1
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