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authorDarren Hart <dvhart@linux.intel.com>2012-11-26 16:29:56 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-11-26 17:41:24 -0800
commitaa10990e028cac3d5e255711fb9fb47e00700e35 (patch)
treedc39cb7cf8f193fb266bf3da618b77ea76a89c2d
parent8ffeb9b0e6369135bf03a073514f571ef10606b9 (diff)
downloadlinaro-lsk-aa10990e028cac3d5e255711fb9fb47e00700e35.tar.gz
futex: avoid wake_futex() for a PI futex_q
Dave Jones reported a bug with futex_lock_pi() that his trinity test exposed. Sometime between queue_me() and taking the q.lock_ptr, the lock_ptr became NULL, resulting in a crash. While futex_wake() is careful to not call wake_futex() on futex_q's with a pi_state or an rt_waiter (which are either waiting for a futex_unlock_pi() or a PI futex_requeue()), futex_wake_op() and futex_requeue() do not perform the same test. Update futex_wake_op() and futex_requeue() to test for q.pi_state and q.rt_waiter and abort with -EINVAL if detected. To ensure any future breakage is caught, add a WARN() to wake_futex() if the same condition is true. This fix has seen 3 hours of testing with "trinity -c futex" on an x86_64 VM with 4 CPUS. [akpm@linux-foundation.org: tidy up the WARN()] Signed-off-by: Darren Hart <dvhart@linux.intel.com> Reported-by: Dave Jones <davej@redat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: John Kacur <jkacur@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/futex.c18
1 files changed, 17 insertions, 1 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 20ef219bbe9..19eb089ca00 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -843,6 +843,9 @@ static void wake_futex(struct futex_q *q)
{
struct task_struct *p = q->task;
+ if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
+ return;
+
/*
* We set q->lock_ptr = NULL _before_ we wake up the task. If
* a non-futex wake up happens on another CPU then the task
@@ -1078,6 +1081,10 @@ retry_private:
plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key1)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
wake_futex(this);
if (++ret >= nr_wake)
break;
@@ -1090,6 +1097,10 @@ retry_private:
op_ret = 0;
plist_for_each_entry_safe(this, next, head, list) {
if (match_futex (&this->key, &key2)) {
+ if (this->pi_state || this->rt_waiter) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
wake_futex(this);
if (++op_ret >= nr_wake2)
break;
@@ -1098,6 +1109,7 @@ retry_private:
ret += op_ret;
}
+out_unlock:
double_unlock_hb(hb1, hb2);
out_put_keys:
put_futex_key(&key2);
@@ -1387,9 +1399,13 @@ retry_private:
/*
* FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
* be paired with each other and no other futex ops.
+ *
+ * We should never be requeueing a futex_q with a pi_state,
+ * which is awaiting a futex_unlock_pi().
*/
if ((requeue_pi && !this->rt_waiter) ||
- (!requeue_pi && this->rt_waiter)) {
+ (!requeue_pi && this->rt_waiter) ||
+ this->pi_state) {
ret = -EINVAL;
break;
}