From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:35512 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753086AbdCTRdm (ORCPT ); Mon, 20 Mar 2017 13:33:42 -0400 Subject: Patch "futex: Fix potential use-after-free in FUTEX_REQUEUE_PI" has been added to the 4.10-stable tree To: peterz@infradead.org, dvhart@linux.intel.com, dvyukov@google.com, gregkh@linuxfoundation.org, tglx@linutronix.de Cc: , From: Date: Mon, 20 Mar 2017 18:33:23 +0100 Message-ID: <149003120319085@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled futex: Fix potential use-after-free in FUTEX_REQUEUE_PI to the 4.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: futex-fix-potential-use-after-free-in-futex_requeue_pi.patch and it can be found in the queue-4.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From c236c8e95a3d395b0494e7108f0d41cf36ec107c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Sat, 4 Mar 2017 10:27:18 +0100 Subject: futex: Fix potential use-after-free in FUTEX_REQUEUE_PI From: Peter Zijlstra commit c236c8e95a3d395b0494e7108f0d41cf36ec107c upstream. While working on the futex code, I stumbled over this potential use-after-free scenario. Dmitry triggered it later with syzkaller. pi_mutex is a pointer into pi_state, which we drop the reference on in unqueue_me_pi(). So any access to that pointer after that is bad. Since other sites already do rt_mutex_unlock() with hb->lock held, see for example futex_lock_pi(), simply move the unlock before unqueue_me_pi(). Reported-by: Dmitry Vyukov Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Darren Hart Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170304093558.801744246@infradead.org Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2813,7 +2813,6 @@ static int futex_wait_requeue_pi(u32 __u { struct hrtimer_sleeper timeout, *to = NULL; struct rt_mutex_waiter rt_waiter; - struct rt_mutex *pi_mutex = NULL; struct futex_hash_bucket *hb; union futex_key key2 = FUTEX_KEY_INIT; struct futex_q q = futex_q_init; @@ -2905,6 +2904,8 @@ static int futex_wait_requeue_pi(u32 __u spin_unlock(q.lock_ptr); } } else { + struct rt_mutex *pi_mutex; + /* * We have been woken up by futex_unlock_pi(), a timeout, or a * signal. futex_unlock_pi() will not destroy the lock_ptr nor @@ -2928,18 +2929,19 @@ static int futex_wait_requeue_pi(u32 __u if (res) ret = (res < 0) ? res : 0; + /* + * If fixup_pi_state_owner() faulted and was unable to handle + * the fault, unlock the rt_mutex and return the fault to + * userspace. + */ + if (ret && rt_mutex_owner(pi_mutex) == current) + rt_mutex_unlock(pi_mutex); + /* Unqueue and drop the lock. */ unqueue_me_pi(&q); } - /* - * If fixup_pi_state_owner() faulted and was unable to handle the - * fault, unlock the rt_mutex and return the fault to userspace. - */ - if (ret == -EFAULT) { - if (pi_mutex && rt_mutex_owner(pi_mutex) == current) - rt_mutex_unlock(pi_mutex); - } else if (ret == -EINTR) { + if (ret == -EINTR) { /* * We've already been requeued, but cannot restart by calling * futex_lock_pi() directly. We could restart this syscall, but Patches currently in stable-queue which might be from peterz@infradead.org are queue-4.10/futex-fix-potential-use-after-free-in-futex_requeue_pi.patch queue-4.10/futex-add-missing-error-handling-to-futex_requeue_pi.patch queue-4.10/x86-perf-fix-cr4.pce-propagation-to-use-active_mm-instead-of-mm.patch queue-4.10/x86-intel_rdt-put-group-node-in-rdtgroup_kn_unlock.patch queue-4.10/locking-rwsem-fix-down_write_killable-for-config_rwsem_generic_spinlock-y.patch queue-4.10/x86-tsc-fix-art-for-tsc_known_freq.patch