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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** 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 <dvhart@xxxxxxxxxxxxxxx> 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 <dvhart@xxxxxxxxxxxxxxx> Reported-by: Dave Jones <davej@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: John Kacur <jkacur@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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 dvhart@xxxxxxxxxxxxxxx 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html