Commit-ID: 0e8f7a5954be13d0c8dcbca3204a9e962498c46e Gitweb: http://git.kernel.org/tip/0e8f7a5954be13d0c8dcbca3204a9e962498c46e Author: Darren Hart <dvh...@linux.intel.com> AuthorDate: Tue, 20 Nov 2012 23:36:45 -0800 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Wed, 21 Nov 2012 21:05:34 +0100
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. Reported-by: Dave Jones <da...@redat.com> Signed-off-by: Darren Hart <dvh...@linux.intel.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: John Kacur <jka...@redhat.com> Cc: sta...@vger.kernel.org Link: http://lkml.kernel.org/r/3b25c8ba053760892871713ff6e81660433f6734.1353483196.git.dvh...@linux.intel.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- kernel/futex.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index 3717e7b..5699b21 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -840,6 +840,11 @@ 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 @@ -1075,6 +1080,10 @@ 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; @@ -1087,6 +1096,10 @@ 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; @@ -1095,6 +1108,7 @@ retry_private: ret += op_ret; } +out_unlock: double_unlock_hb(hb1, hb2); out_put_keys: put_futex_key(&key2); @@ -1384,9 +1398,13 @@ 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; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
