Revision 7e1d90f60a0d501c8503e636942ca704a454d910 authored by Daniel Mentz on 14 August 2017, 21:46:01 UTC, committed by Takashi Iwai on 15 August 2017, 06:02:35 UTC
commit 4842e98f26dd80be3623c4714a244ba52ea096a8 ("ALSA: seq: Fix race at creating a queue") attempted to fix a race reported by syzkaller. That fix has been described as follows: " When a sequencer queue is created in snd_seq_queue_alloc(),it adds the new queue element to the public list before referencing it. Thus the queue might be deleted before the call of snd_seq_queue_use(), and it results in the use-after-free error, as spotted by syzkaller. The fix is to reference the queue object at the right time. " Even with that fix in place, syzkaller reported a use-after-free error. It specifically pointed to the last instruction "return q->queue" in snd_seq_queue_alloc(). The pointer q is being used after kfree() has been called on it. It turned out that there is still a small window where a race can happen. The window opens at snd_seq_ioctl_create_queue()->snd_seq_queue_alloc()->queue_list_add() and closes at snd_seq_ioctl_create_queue()->queueptr()->snd_use_lock_use(). Between these two calls, a different thread could delete the queue and possibly re-create a different queue in the same location in queue_list. This change prevents this situation by calling snd_use_lock_use() from snd_seq_queue_alloc() prior to calling queue_list_add(). It is then the caller's responsibility to call snd_use_lock_free(&q->use_lock). Fixes: 4842e98f26dd ("ALSA: seq: Fix race at creating a queue") Reported-by: Dmitry Vyukov <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Daniel Mentz <danielmentz@google.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
1 parent 8df4b00
File | Mode | Size |
---|---|---|
BUGS-parport | -rw-r--r-- | 319 bytes |
Kconfig | -rw-r--r-- | 5.4 KB |
Makefile | -rw-r--r-- | 693 bytes |
TODO-parport | -rw-r--r-- | 594 bytes |
daisy.c | -rw-r--r-- | 12.3 KB |
ieee1284.c | -rw-r--r-- | 22.6 KB |
ieee1284_ops.c | -rw-r--r-- | 23.3 KB |
multiface.h | -rw-r--r-- | 387 bytes |
parport_amiga.c | -rw-r--r-- | 6.3 KB |
parport_atari.c | -rw-r--r-- | 5.4 KB |
parport_ax88796.c | -rw-r--r-- | 9.3 KB |
parport_cs.c | -rw-r--r-- | 5.5 KB |
parport_gsc.c | -rw-r--r-- | 11.0 KB |
parport_gsc.h | -rw-r--r-- | 6.1 KB |
parport_ip32.c | -rw-r--r-- | 67.0 KB |
parport_mfc3.c | -rw-r--r-- | 9.9 KB |
parport_pc.c | -rw-r--r-- | 85.5 KB |
parport_serial.c | -rw-r--r-- | 20.1 KB |
parport_sunbpp.c | -rw-r--r-- | 9.3 KB |
probe.c | -rw-r--r-- | 7.4 KB |
procfs.c | -rw-r--r-- | 12.6 KB |
share.c | -rw-r--r-- | 36.8 KB |
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...