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 6.1-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-6.1 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>
commit 56b88b50565cd8b946a2d00b0c83927b7ebb055e upstream.
Takes rwsem lock inside snd_ctl_elem_read instead of snd_ctl_elem_read_user
like it was done for write in commit 1fa4445f9adf1 ("ALSA: control - introduce
snd_ctl_notify_one() helper"). Doing this way we are also fixing the following
locking issue happening in the compat path which can be easily triggered and
turned into an use-after-free.
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:
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.
Cc: stable@xxxxxxxxxx # 5.13+
Signed-off-by: Clement Lecigne <clecigne@xxxxxxxxxx>
Reviewed-by: Jaroslav Kysela <perex@xxxxxxxx>
Link: https://lore.kernel.org/r/20230113120745.25464-1-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/control.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -1203,14 +1203,19 @@ static int snd_ctl_elem_read(struct snd_
const u32 pattern = 0xdeadbeef;
int ret;
+ down_read(&card->controls_rwsem);
kctl = snd_ctl_find_id(card, &control->id);
- if (kctl == NULL)
- return -ENOENT;
+ if (kctl == NULL) {
+ ret = -ENOENT;
+ goto unlock;
+ }
index_offset = snd_ctl_get_ioff(kctl, &control->id);
vd = &kctl->vd[index_offset];
- if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || kctl->get == NULL)
- return -EPERM;
+ if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_READ) || kctl->get == NULL) {
+ ret = -EPERM;
+ goto unlock;
+ }
snd_ctl_build_ioff(&control->id, kctl, index_offset);
@@ -1220,7 +1225,7 @@ static int snd_ctl_elem_read(struct snd_
info.id = control->id;
ret = __snd_ctl_elem_info(card, kctl, &info, NULL);
if (ret < 0)
- return ret;
+ goto unlock;
#endif
if (!snd_ctl_skip_validation(&info))
@@ -1230,7 +1235,7 @@ static int snd_ctl_elem_read(struct snd_
ret = kctl->get(kctl, control);
snd_power_unref(card);
if (ret < 0)
- return ret;
+ goto unlock;
if (!snd_ctl_skip_validation(&info) &&
sanity_check_elem_value(card, control, &info, pattern) < 0) {
dev_err(card->dev,
@@ -1238,8 +1243,11 @@ static int snd_ctl_elem_read(struct snd_
control->id.iface, control->id.device,
control->id.subdevice, control->id.name,
control->id.index);
- return -EINVAL;
+ ret = -EINVAL;
+ goto unlock;
}
+unlock:
+ up_read(&card->controls_rwsem);
return ret;
}
@@ -1253,9 +1261,7 @@ static int snd_ctl_elem_read_user(struct
if (IS_ERR(control))
return PTR_ERR(control);
- down_read(&card->controls_rwsem);
result = snd_ctl_elem_read(card, control);
- up_read(&card->controls_rwsem);
if (result < 0)
goto error;
Patches currently in stable-queue which might be from clecigne@xxxxxxxxxx are
queue-6.1/alsa-pcm-move-rwsem-lock-inside-snd_ctl_elem_read-to-prevent-uaf.patch
