linux-toradex.git/sound/drivers/dummy.c, branch v4.10

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

2016-06-24T13:18:32+00:00

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

ALSA: dummy: Implement timer backend switching more safely

2016-02-08T07:15:35+00:00

Currently the selected timer backend is referred at any moment from
the running PCM callbacks.  When the backend is switched, it's
possible to lead to inconsistency from the running backend.  This was
pointed by syzkaller fuzzer, and the commit [7ee96216c31a: ALSA:
dummy: Disable switching timer backend via sysfs] disabled the dynamic
switching for avoiding the crash.

This patch improves the handling of timer backend switching.  It keeps
the reference to the selected backend during the whole operation of an
opened stream so that it won't be changed by other streams.

Together with this change, the hrtimer parameter is reenabled as
writable now.

NOTE: this patch also turned out to fix the still remaining race.
Namely, ops was still replaced dynamically at dummy_pcm_open:

  static int dummy_pcm_open(struct snd_pcm_substream *substream)
  {
  ....
          dummy->timer_ops = &dummy_systimer_ops;
          if (hrtimer)
                  dummy->timer_ops = &dummy_hrtimer_ops;

Since dummy->timer_ops is common among all streams, and when the
replacement happens during accesses of other streams, it may lead to a
crash.  This was actually triggered by syzkaller fuzzer and KASAN.

This patch rewrites the code not to use the ops shared by all streams
any longer, too.

BugLink: http://lkml.kernel.org/r/CACT4Y+aZ+xisrpuM6cOXbL21DuM0yVxPYXf4cD4Md9uw0C3dBQ@mail.gmail.com
Reported-by: Dmitry Vyukov 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: dummy: Disable switching timer backend via sysfs

2016-01-28T07:13:54+00:00

ALSA dummy driver can switch the timer backend between system timer
and hrtimer via its hrtimer module option.  This can be also switched
dynamically via sysfs, but it may lead to a memory corruption when
switching is done while a PCM stream is running; the stream instance
for the newly switched timer method tries to access the memory that
was allocated by another timer method although the sizes differ.

As the simplest fix, this patch just disables the switch via sysfs by
dropping the writable bit.

BugLink: http://lkml.kernel.org/r/CACT4Y+ZGEeEBntHW5WHn2GoeE0G_kRrCmUh6=dWyy-wfzvuJLg@mail.gmail.com
Reported-by: Dmitry Vyukov 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: dummy: constify dummy_timer_ops structures

2015-12-30T21:49:42+00:00

The dummy_timer_ops structures are never modified, so declare them as
const.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall 
Signed-off-by: Takashi Iwai

ALSA: dummy: Replace CONFIG_PROC_FS with CONFIG_SND_PROC_FS

2015-05-29T05:47:50+00:00

Although there shouldn't be a problem in practice (the compiler should
handle well), it's better to follow to the new Kconfig.

Signed-off-by: Takashi Iwai

ALSA: dummy: make local data static

2015-05-26T10:59:26+00:00

Add missing prefix to make some local data static.

Spotted by sparse:
  sound/drivers/dummy.c:159:20: warning: symbol 'model_emu10k1' was not declared. Should it be static?
  sound/drivers/dummy.c:165:20: warning: symbol 'model_rme9652' was not declared. Should it be static?
  ....

Signed-off-by: Takashi Iwai

ALSA: dummy: use setup_timer and mod_timer

2015-01-19T09:49:52+00:00

Use setup_timer and mod_timer instead of structure assignments as it
is the preferred way to setup and set the timer.

Signed-off-by: Roman Kollar 
Signed-off-by: Jiri Slaby 
Signed-off-by: Takashi Iwai

ALSA: drivers: drop owner assignment from platform_drivers

2014-10-20T14:21:59+00:00

A platform_driver does not need to set an owner, it will be populated by the
driver core.

Signed-off-by: Wolfram Sang

ALSA: drivers: Convert to snd_card_new() with a device pointer

2014-02-12T09:58:20+00:00

Also remove superfluous snd_card_set_dev() calls.

Signed-off-by: Takashi Iwai

ALSA: replace strict_strto() with kstrto()

2013-07-21T09:56:18+00:00

The usage of strict_strto*() is not preferred, because
strict_strto*() is obsolete. Thus, kstrto*() should be
used.

Signed-off-by: Jingoo Han 
Signed-off-by: Takashi Iwai