3.5.7.2 -stable review patch. If anyone has any objections, please let me know.
------------------ From: Darren Hart <[email protected]> commit aa10990e028cac3d5e255711fb9fb47e00700e35 upstream. 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. [[email protected]: tidy up the WARN()] 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]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Herton Ronaldo Krzesinski <[email protected]> --- kernel/futex.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index 20ef219..19eb089 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; } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
