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authorTakashi Iwai <tiwai@suse.de>2017-10-29 11:02:04 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-08 10:06:27 +0100
commit70358782743fbc2b2fa26b4e7370b359350cfba3 (patch)
tree72b09537407e704dd2f32ff3c0527d1d528538f3
parent27e68f1bca91a7f69808c8641f03c66cca2bb365 (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>
-rw-r--r--sound/core/timer_compat.c17
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;
+}