This is a note to let you know that I've just added the patch titled
ALSA: timer: Add missing mutex lock for compat ioctls
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-timer-add-missing-mutex-lock-for-compat-ioctls.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 79fb0518fec8c8b4ea7f1729f54f293724b3dbb0 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Sun, 29 Oct 2017 11:02:04 +0100
Subject: ALSA: timer: Add missing mutex lock for compat ioctls
From: Takashi Iwai <tiwai@xxxxxxx>
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@xxxxxxxxxx
Reported-by: syzbot <bot+e5f3c9783e7048a74233054febbe9f1bdf54b6da@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/timer_compat.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)
--- 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(
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(
}
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;
+}
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-4.4/alsa-seq-fix-nested-rwsem-annotation-for-lockdep-splat.patch
queue-4.4/alsa-timer-add-missing-mutex-lock-for-compat-ioctls.patch