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Patch "ALSA: dummy: Fix a use-after-free at closing" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Jul 25, 2016

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This is a note to let you know that I've just added the patch titled

ALSA: dummy: Fix a use-after-free at closing

to the 4.4-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:
alsa-dummy-fix-a-use-after-free-at-closing.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d5dbbe6569481bf12dcbe3e12cff72c5f78d272c Mon Sep 17 00:00:00 2001

From: Takashi Iwai <[email protected]>
Date: Fri, 24 Jun 2016 15:15:26 +0200
Subject: ALSA: dummy: Fix a use-after-free at closing

From: Takashi Iwai <[email protected]>

commit d5dbbe6569481bf12dcbe3e12cff72c5f78d272c upstream.

syzkaller fuzzer spotted a potential use-after-free case in snd-dummy driver when hrtimer is used as backend:

Quoted 30 lines

==================================================================

BUG: KASAN: use-after-free in rb_erase+0x1b17/0x2010 at addr ffff88005e5b6f68
 Read of size 8 by task syz-executor/8984
=============================================================================

BUG kmalloc-192 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------

Disabling lock debugging due to kernel taint
INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446705582212484632
....
[< none >] dummy_hrtimer_create+0x49/0x1a0 sound/drivers/dummy.c:464
....
INFO: Freed in 0xfffd8e09 age=18446705496313138713 cpu=2164287125 pid=-1
[< none >] dummy_hrtimer_free+0x68/0x80 sound/drivers/dummy.c:481
....

Call Trace:
 [<ffffffff8179e59e>] __asan_report_load8_noabort+0x3e/0x40 mm/kasan/report.c:333
 [<     inline     >] rb_set_parent include/linux/rbtree_augmented.h:111
 [<     inline     >] __rb_erase_augmented include/linux/rbtree_augmented.h:218
 [<ffffffff82ca5787>] rb_erase+0x1b17/0x2010 lib/rbtree.c:427
 [<ffffffff82cb02e8>] timerqueue_del+0x78/0x170 lib/timerqueue.c:86
 [<ffffffff814d0c80>] __remove_hrtimer+0x90/0x220 kernel/time/hrtimer.c:903
 [<     inline     >] remove_hrtimer kernel/time/hrtimer.c:945
 [<ffffffff814d23da>] hrtimer_try_to_cancel+0x22a/0x570 kernel/time/hrtimer.c:1046
 [<ffffffff814d2742>] hrtimer_cancel+0x22/0x40 kernel/time/hrtimer.c:1066
 [<ffffffff85420531>] dummy_hrtimer_stop+0x91/0xb0 sound/drivers/dummy.c:417
 [<ffffffff854228bf>] dummy_pcm_trigger+0x17f/0x1e0 sound/drivers/dummy.c:507
 [<ffffffff85392170>] snd_pcm_do_stop+0x160/0x1b0 sound/core/pcm_native.c:1106
 [<ffffffff85391b26>] snd_pcm_action_single+0x76/0x120 sound/core/pcm_native.c:956
 [<ffffffff85391e01>] snd_pcm_action+0x231/0x290 sound/core/pcm_native.c:974
Quoted 8 lines
 [<     inline     >] snd_pcm_stop sound/core/pcm_native.c:1139
 [<ffffffff8539754d>] snd_pcm_drop+0x12d/0x1d0 sound/core/pcm_native.c:1784
 [<ffffffff8539d3be>] snd_pcm_common_ioctl1+0xfae/0x2150 sound/core/pcm_native.c:2805
 [<ffffffff8539ee91>] snd_pcm_capture_ioctl1+0x2a1/0x5e0 sound/core/pcm_native.c:2976
 [<ffffffff8539f2ec>] snd_pcm_kernel_ioctl+0x11c/0x160 sound/core/pcm_native.c:3020
 [<ffffffff853d9a44>] snd_pcm_oss_sync+0x3a4/0xa30 sound/core/oss/pcm_oss.c:1693
 [<ffffffff853da27d>] snd_pcm_oss_release+0x1ad/0x280 sound/core/oss/pcm_oss.c:2483
 .....

A workaround is to call hrtimer_cancel() in dummy_hrtimer_sync() which is called certainly before other blocking ops.

Reported-by Dmitry Vyukov <[email protected]>
Tested-by Dmitry Vyukov <[email protected]>
Signed-off-by Takashi Iwai <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 sound/drivers/dummy.c |    1 +
 1 file changed, 1 insertion(+)
sound/drivers/dummy.c +1 -0
@@ -420,6 +420,7 @@ static int dummy_hrtimer_stop(struct snd
 
 static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm)
 {
+	hrtimer_cancel(&dpcm->timer);
 	tasklet_kill(&dpcm->tasklet);
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/alsa-hda-fix-the-headset-mic-jack-detection-on-dell-machine.patch queue-4.4/alsa-ctl-stop-notification-after-disconnection.patch queue-4.4/alsa-dummy-fix-a-use-after-free-at-closing.patch queue-4.4/alsa-timer-fix-negative-queue-usage-by-racy-accesses.patch queue-4.4/alsa-hda-fix-use-after-free-after-module-unload.patch queue-4.4/alsa-hda-realtek-add-new-pin-definition-in-alc225-pin-quirk-table.patch queue-4.4/alsa-hda-add-pci-id-for-kabylake-h.patch queue-4.4/alsa-pcm-free-chmap-at-pcm-free-callback-too.patch queue-4.4/alsa-au88x0-fix-calculation-in-vortex_wtdma_bufshift.patch queue-4.4/alsa-hda-realtek-add-lenovo-l460-to-docking-unit-fixup.patch queue-4.4/alsa-echoaudio-fix-memory-allocation.patch queue-4.4/alsa-hda-realtek-add-two-more-thinkpad-ids-5050-5053-for-tpt460-fixup.patch queue-4.4/alsa-hda-fix-read-before-array-start.patch queue-4.4/alsa-hda-add-amd-stoney-pci-id-with-proper-driver-caps.patch