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 3.18-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-3.18 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-3.18/alsa-seq-fix-nested-rwsem-annotation-for-lockdep-splat.patch queue-3.18/alsa-timer-add-missing-mutex-lock-for-compat-ioctls.patch