lkml.org 
[lkml]   [2021]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.14 055/251] ALSA: mixer: oss: Fix racy access to slots
Date
From: Takashi Iwai <tiwai@suse.de>

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@syzkaller.appspotmail.com
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/00000000000036adc005ceca9175@google.com
Link: https://lore.kernel.org/r/20211020164846.922-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/core/oss/mixer_oss.c | 43 +++++++++++++++++++++++++++++++++----------
1 file changed, 33 insertions(+), 10 deletions(-)

--- a/sound/core/oss/mixer_oss.c
+++ b/sound/core/oss/mixer_oss.c
@@ -145,11 +145,13 @@ static int snd_mixer_oss_devmask(struct

if (mixer == NULL)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
for (chn = 0; chn < 31; chn++) {
pslot = &mixer->slots[chn];
if (pslot->put_volume || pslot->put_recsrc)
result |= 1 << chn;
}
+ mutex_unlock(&mixer->reg_mutex);
return result;
}

@@ -161,11 +163,13 @@ static int snd_mixer_oss_stereodevs(stru

if (mixer == NULL)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
for (chn = 0; chn < 31; chn++) {
pslot = &mixer->slots[chn];
if (pslot->put_volume && pslot->stereo)
result |= 1 << chn;
}
+ mutex_unlock(&mixer->reg_mutex);
return result;
}

@@ -176,6 +180,7 @@ static int snd_mixer_oss_recmask(struct

if (mixer == NULL)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
if (mixer->put_recsrc && mixer->get_recsrc) { /* exclusive */
result = mixer->mask_recsrc;
} else {
@@ -187,6 +192,7 @@ static int snd_mixer_oss_recmask(struct
result |= 1 << chn;
}
}
+ mutex_unlock(&mixer->reg_mutex);
return result;
}

@@ -197,11 +203,12 @@ static int snd_mixer_oss_get_recsrc(stru

if (mixer == NULL)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
if (mixer->put_recsrc && mixer->get_recsrc) { /* exclusive */
- int err;
unsigned int index;
- if ((err = mixer->get_recsrc(fmixer, &index)) < 0)
- return err;
+ result = mixer->get_recsrc(fmixer, &index);
+ if (result < 0)
+ goto unlock;
result = 1 << index;
} else {
struct snd_mixer_oss_slot *pslot;
@@ -216,7 +223,10 @@ static int snd_mixer_oss_get_recsrc(stru
}
}
}
- return mixer->oss_recsrc = result;
+ mixer->oss_recsrc = result;
+ unlock:
+ mutex_unlock(&mixer->reg_mutex);
+ return result;
}

static int snd_mixer_oss_set_recsrc(struct snd_mixer_oss_file *fmixer, int recsrc)
@@ -229,6 +239,7 @@ static int snd_mixer_oss_set_recsrc(stru

if (mixer == NULL)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
if (mixer->get_recsrc && mixer->put_recsrc) { /* exclusive input */
if (recsrc & ~mixer->oss_recsrc)
recsrc &= ~mixer->oss_recsrc;
@@ -254,6 +265,7 @@ static int snd_mixer_oss_set_recsrc(stru
}
}
}
+ mutex_unlock(&mixer->reg_mutex);
return result;
}

@@ -265,6 +277,7 @@ static int snd_mixer_oss_get_volume(stru

if (mixer == NULL || slot > 30)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
pslot = &mixer->slots[slot];
left = pslot->volume[0];
right = pslot->volume[1];
@@ -272,15 +285,21 @@ static int snd_mixer_oss_get_volume(stru
result = pslot->get_volume(fmixer, pslot, &left, &right);
if (!pslot->stereo)
right = left;
- if (snd_BUG_ON(left < 0 || left > 100))
- return -EIO;
- if (snd_BUG_ON(right < 0 || right > 100))
- return -EIO;
+ if (snd_BUG_ON(left < 0 || left > 100)) {
+ result = -EIO;
+ goto unlock;
+ }
+ if (snd_BUG_ON(right < 0 || right > 100)) {
+ result = -EIO;
+ goto unlock;
+ }
if (result >= 0) {
pslot->volume[0] = left;
pslot->volume[1] = right;
result = (left & 0xff) | ((right & 0xff) << 8);
}
+ unlock:
+ mutex_unlock(&mixer->reg_mutex);
return result;
}

@@ -293,6 +312,7 @@ static int snd_mixer_oss_set_volume(stru

if (mixer == NULL || slot > 30)
return -EIO;
+ mutex_lock(&mixer->reg_mutex);
pslot = &mixer->slots[slot];
if (left > 100)
left = 100;
@@ -303,10 +323,13 @@ static int snd_mixer_oss_set_volume(stru
if (pslot->put_volume)
result = pslot->put_volume(fmixer, pslot, left, right);
if (result < 0)
- return result;
+ goto unlock;
pslot->volume[0] = left;
pslot->volume[1] = right;
- return (left & 0xff) | ((right & 0xff) << 8);
+ result = (left & 0xff) | ((right & 0xff) << 8);
+ unlock:
+ mutex_lock(&mixer->reg_mutex);
+ return result;
}

static int snd_mixer_oss_ioctl1(struct snd_mixer_oss_file *fmixer, unsigned int cmd, unsigned long arg)

\
 
 \ /
  Last update: 2021-11-24 13:35    [W:0.685 / U:0.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site