From d5dbbe6569481bf12dcbe3e12cff72c5f78d272c Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 24 Jun 2016 15:15:26 +0200 Subject: ALSA: dummy: Fix a use-after-free at closing syzkaller fuzzer spotted a potential use-after-free case in snd-dummy driver when hrtimer is used as backend: > ================================================================== > 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: > [] __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 > [] rb_erase+0x1b17/0x2010 lib/rbtree.c:427 > [] timerqueue_del+0x78/0x170 lib/timerqueue.c:86 > [] __remove_hrtimer+0x90/0x220 kernel/time/hrtimer.c:903 > [< inline >] remove_hrtimer kernel/time/hrtimer.c:945 > [] hrtimer_try_to_cancel+0x22a/0x570 kernel/time/hrtimer.c:1046 > [] hrtimer_cancel+0x22/0x40 kernel/time/hrtimer.c:1066 > [] dummy_hrtimer_stop+0x91/0xb0 sound/drivers/dummy.c:417 > [] dummy_pcm_trigger+0x17f/0x1e0 sound/drivers/dummy.c:507 > [] snd_pcm_do_stop+0x160/0x1b0 sound/core/pcm_native.c:1106 > [] snd_pcm_action_single+0x76/0x120 sound/core/pcm_native.c:956 > [] snd_pcm_action+0x231/0x290 sound/core/pcm_native.c:974 > [< inline >] snd_pcm_stop sound/core/pcm_native.c:1139 > [] snd_pcm_drop+0x12d/0x1d0 sound/core/pcm_native.c:1784 > [] snd_pcm_common_ioctl1+0xfae/0x2150 sound/core/pcm_native.c:2805 > [] snd_pcm_capture_ioctl1+0x2a1/0x5e0 sound/core/pcm_native.c:2976 > [] snd_pcm_kernel_ioctl+0x11c/0x160 sound/core/pcm_native.c:3020 > [] snd_pcm_oss_sync+0x3a4/0xa30 sound/core/oss/pcm_oss.c:1693 > [] 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 Tested-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/drivers/dummy.c | 1 + 1 file changed, 1 insertion(+) diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index c0f8f613f1f1..172dacd925f5 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -420,6 +420,7 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) { + hrtimer_cancel(&dpcm->timer); tasklet_kill(&dpcm->tasklet); } -- cgit v1.2.3