diff options
| author | Takashi Iwai <tiwai@suse.de> | 2017-10-29 11:02:04 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-11-08 10:06:27 +0100 |
| commit | 70358782743fbc2b2fa26b4e7370b359350cfba3 (patch) | |
| tree | 72b09537407e704dd2f32ff3c0527d1d528538f3 /sound | |
| parent | 27e68f1bca91a7f69808c8641f03c66cca2bb365 (diff) | |
ALSA: timer: Add missing mutex lock for compat ioctls
commit 79fb0518fec8c8b4ea7f1729f54f293724b3dbb0 upstream.
The races among ioctl and other operations were protected by the
commit af368027a49a ("ALSA: timer: Fix race among timer ioctls") and
later fixes, but one code path was forgotten in the scenario: the
32bit compat ioctl. As syzkaller recently spotted, a very similar
use-after-free may happen with the combination of compat ioctls.
The fix is simply to apply the same ioctl_lock to the compat_ioctl
callback, too.
Fixes: af368027a49a ("ALSA: timer: Fix race among timer ioctls")
Reference: http://lkml.kernel.org/r/089e082686ac9b482e055c832617@google.com
Reported-by: syzbot <bot+e5f3c9783e7048a74233054febbe9f1bdf54b6da@syzkaller.appspotmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
| -rw-r--r-- | sound/core/timer_compat.c | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/sound/core/timer_compat.c b/sound/core/timer_compat.c index 2e908225d754..0b4b028e8e98 100644 --- a/sound/core/timer_compat.c +++ b/sound/core/timer_compat.c @@ -106,7 +106,8 @@ enum { #endif /* CONFIG_X86_X32 */ }; -static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) +static long __snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) { void __user *argp = compat_ptr(arg); @@ -127,7 +128,7 @@ static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, uns case SNDRV_TIMER_IOCTL_PAUSE: case SNDRV_TIMER_IOCTL_PAUSE_OLD: case SNDRV_TIMER_IOCTL_NEXT_DEVICE: - return snd_timer_user_ioctl(file, cmd, (unsigned long)argp); + return __snd_timer_user_ioctl(file, cmd, (unsigned long)argp); case SNDRV_TIMER_IOCTL_INFO32: return snd_timer_user_info_compat(file, argp); case SNDRV_TIMER_IOCTL_STATUS32: @@ -139,3 +140,15 @@ static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, uns } return -ENOIOCTLCMD; } + +static long snd_timer_user_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct snd_timer_user *tu = file->private_data; + long ret; + + mutex_lock(&tu->ioctl_lock); + ret = __snd_timer_user_ioctl_compat(file, cmd, arg); + mutex_unlock(&tu->ioctl_lock); + return ret; +} |