The patch titled
Subject: futex: avoid wake_futex() for a PI futex_q
has been added to the -mm tree. Its filename is
futex-avoid-wake_futex-for-a-pi-futex_q.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Darren Hart <[email protected]>
Subject: 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.
Signed-off-by: Darren Hart <[email protected]>
Reported-by: Dave Jones <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John Kacur <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
kernel/futex.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff -puN kernel/futex.c~futex-avoid-wake_futex-for-a-pi-futex_q kernel/futex.c
--- a/kernel/futex.c~futex-avoid-wake_futex-for-a-pi-futex_q
+++ a/kernel/futex.c
@@ -843,6 +843,11 @@ static void wake_futex(struct futex_q *q
{
struct task_struct *p = q->task;
+ if (q->pi_state || q->rt_waiter) {
+ WARN(1, "%s: refusing to wake PI futex\n", __FUNCTION__);
+ 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 +1083,10 @@ 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 +1099,10 @@ 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 +1111,7 @@ retry_private:
ret += op_ret;
}
+out_unlock:
double_unlock_hb(hb1, hb2);
out_put_keys:
put_futex_key(&key2);
@@ -1387,9 +1401,13 @@ 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;
}
_
Patches currently in -mm which might be from [email protected] are
linux-next.patch
futex-avoid-wake_futex-for-a-pi-futex_q.patch
futex-avoid-wake_futex-for-a-pi-futex_q-fix.patch
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