Re: [PATCH stable-5.4.y 1/2] ALSA: mixer: oss: Fix racy access to slots

[Greg Kroah-Hartman]

On Sat, Nov 13, 2021 at 04:38:45PM +0100, Takashi Iwai wrote:
> commit 411cef6adfb38a5bb6bd9af3941b28198e7fb680 upstream.
> 
> The OSS mixer can reassign the mapping slots dynamically via proc
> file.  Although the addition and deletion of those slots are protected
> by mixer->reg_mutex, the access to slots aren't, hence this may cause
> UAF when the slots in use are deleted concurrently.
> 
> This patch applies the mixer->reg_mutex in all appropriate code paths
> (i.e. the ioctl functions) that may access slots.
> 
> Reported-by: syzbot+9988f17cf72a1045a189@xxxxxxxxxxxxxxxxxxxxxxxxx
> Reviewed-by: Jaroslav Kysela <perex@xxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/r/00000000000036adc005ceca9175@xxxxxxxxxx
> Link: https://lore.kernel.org/r/20211020164846.922-1-tiwai@xxxxxxx
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> ---
> 
> Please apply to older stable kernels, too

Both now queued up, thanks!

greg k-h