This is a note to let you know that I've just added the patch titled
ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF
to the 5.10-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-pcm-move-rwsem-lock-inside-snd_ctl_elem_read-to-prevent-uaf.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 56b88b50565cd8b946a2d00b0c83927b7ebb055e Mon Sep 17 00:00:00 2001
From: Clement Lecigne <clecigne@xxxxxxxxxx>
Date: Fri, 13 Jan 2023 13:07:45 +0100
Subject: ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF
From: Clement Lecigne <clecigne@xxxxxxxxxx>
[ Note: this is a fix that works around the bug equivalently as the
two upstream commits:
1fa4445f9adf ("ALSA: control - introduce snd_ctl_notify_one() helper")
56b88b50565c ("ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF")
but in a simpler way to fit with older stable trees -- tiwai ]
Add missing locking in ctl_elem_read_user/ctl_elem_write_user which can be
easily triggered and turned into an use-after-free.
Example code paths with SNDRV_CTL_IOCTL_ELEM_READ:
64-bits:
snd_ctl_ioctl
snd_ctl_elem_read_user
[takes controls_rwsem]
snd_ctl_elem_read [lock properly held, all good]
[drops controls_rwsem]
32-bits (compat):
snd_ctl_ioctl_compat
snd_ctl_elem_write_read_compat
ctl_elem_write_read
snd_ctl_elem_read [missing lock, not good]
CVE-2023-0266 was assigned for this issue.
Signed-off-by: Clement Lecigne <clecigne@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx # 5.12 and older
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Reviewed-by: Jaroslav Kysela <perex@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/control_compat.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/sound/core/control_compat.c
+++ b/sound/core/control_compat.c
@@ -304,7 +304,9 @@ static int ctl_elem_read_user(struct snd
err = snd_power_wait(card, SNDRV_CTL_POWER_D0);
if (err < 0)
goto error;
+ down_read(&card->controls_rwsem);
err = snd_ctl_elem_read(card, data);
+ up_read(&card->controls_rwsem);
if (err < 0)
goto error;
err = copy_ctl_value_to_user(userdata, valuep, data, type, count);
@@ -332,7 +334,9 @@ static int ctl_elem_write_user(struct sn
err = snd_power_wait(card, SNDRV_CTL_POWER_D0);
if (err < 0)
goto error;
+ down_write(&card->controls_rwsem);
err = snd_ctl_elem_write(card, file, data);
+ up_write(&card->controls_rwsem);
if (err < 0)
goto error;
err = copy_ctl_value_to_user(userdata, valuep, data, type, count);
Patches currently in stable-queue which might be from clecigne@xxxxxxxxxx are
queue-5.10/alsa-pcm-move-rwsem-lock-inside-snd_ctl_elem_read-to-prevent-uaf.patch
