138 lines
4.9 KiB
Diff
138 lines
4.9 KiB
Diff
From aef881da47f3c07173c5357b36a45fc4b754eb55 Mon Sep 17 00:00:00 2001
|
|
From: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
|
|
Date: Wed, 27 May 2026 17:21:48 +0000
|
|
Subject: [PATCH] ALSA: aloop: Fix peer runtime UAF during format-change stop
|
|
MIME-Version: 1.0
|
|
Content-Type: text/plain; charset=UTF-8
|
|
Content-Transfer-Encoding: 8bit
|
|
|
|
JIRA: https://redhat.atlassian.net/browse/RHEL-179311
|
|
CVE: CVE-2026-46090
|
|
Backported from tree(s): linux
|
|
|
|
commit e5c33cdc6f402eab8abd36ecf436b22c9d3a8aff
|
|
Author: Cássio Gabriel <cassiogabrielcontato@gmail.com>
|
|
Date: Fri Apr 24 09:48:41 2026 -0300
|
|
|
|
ALSA: aloop: Fix peer runtime UAF during format-change stop
|
|
|
|
loopback_check_format() may stop the capture side when playback starts
|
|
with parameters that no longer match a running capture stream. Commit
|
|
826af7fa62e3 ("ALSA: aloop: Fix racy access at PCM trigger") moved
|
|
the peer lookup under cable->lock, but the actual snd_pcm_stop() still
|
|
runs after dropping that lock.
|
|
|
|
A concurrent close can clear the capture entry from cable->streams[] and
|
|
detach or free its runtime while the playback trigger path still holds a
|
|
stale peer substream pointer.
|
|
|
|
Keep a per-cable count of in-flight peer stops before dropping
|
|
cable->lock, and make free_cable() wait for those stops before
|
|
detaching the runtime. This preserves the existing behavior while
|
|
making the peer runtime lifetime explicit.
|
|
|
|
Reported-by: syzbot+8fa95c41eafbc9d2ff6f@syzkaller.appspotmail.com
|
|
Closes: https://syzkaller.appspot.com/bug?extid=8fa95c41eafbc9d2ff6f
|
|
Fixes: 597603d615d2 ("ALSA: introduce the snd-aloop module for the PCM loopback")
|
|
Cc: stable@vger.kernel.org
|
|
Suggested-by: Takashi Iwai <tiwai@suse.com>
|
|
Signed-off-by: Cássio Gabriel <cassiogabrielcontato@gmail.com>
|
|
Link: https://patch.msgid.link/20260424-alsa-aloop-peer-stop-uaf-v2-1-94e68101db8a@gmail.com
|
|
Signed-off-by: Takashi Iwai <tiwai@suse.de>
|
|
|
|
Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
|
|
|
|
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
|
|
index aa0d2fcb1a18..a37a1695f51c 100644
|
|
--- a/sound/drivers/aloop.c
|
|
+++ b/sound/drivers/aloop.c
|
|
@@ -99,6 +99,9 @@ struct loopback_ops {
|
|
struct loopback_cable {
|
|
spinlock_t lock;
|
|
struct loopback_pcm *streams[2];
|
|
+ /* in-flight peer stops running outside cable->lock */
|
|
+ atomic_t stop_count;
|
|
+ wait_queue_head_t stop_wait;
|
|
struct snd_pcm_hardware hw;
|
|
/* flags */
|
|
unsigned int valid;
|
|
@@ -366,8 +369,11 @@ static int loopback_check_format(struct loopback_cable *cable, int stream)
|
|
return 0;
|
|
if (stream == SNDRV_PCM_STREAM_CAPTURE)
|
|
return -EIO;
|
|
- else if (cruntime->state == SNDRV_PCM_STATE_RUNNING)
|
|
+ else if (cruntime->state == SNDRV_PCM_STATE_RUNNING) {
|
|
+ /* close must not free the peer runtime below */
|
|
+ atomic_inc(&cable->stop_count);
|
|
stop_capture = true;
|
|
+ }
|
|
}
|
|
|
|
setup = get_setup(dpcm_play);
|
|
@@ -396,8 +402,11 @@ static int loopback_check_format(struct loopback_cable *cable, int stream)
|
|
}
|
|
}
|
|
|
|
- if (stop_capture)
|
|
+ if (stop_capture) {
|
|
snd_pcm_stop(dpcm_capt->substream, SNDRV_PCM_STATE_DRAINING);
|
|
+ if (atomic_dec_and_test(&cable->stop_count))
|
|
+ wake_up(&cable->stop_wait);
|
|
+ }
|
|
|
|
return 0;
|
|
}
|
|
@@ -1049,23 +1058,29 @@ static void free_cable(struct snd_pcm_substream *substream)
|
|
struct loopback *loopback = substream->private_data;
|
|
int dev = get_cable_index(substream);
|
|
struct loopback_cable *cable;
|
|
+ struct loopback_pcm *dpcm;
|
|
+ bool other_alive;
|
|
|
|
cable = loopback->cables[substream->number][dev];
|
|
if (!cable)
|
|
return;
|
|
- if (cable->streams[!substream->stream]) {
|
|
- /* other stream is still alive */
|
|
- guard(spinlock_irq)(&cable->lock);
|
|
- cable->streams[substream->stream] = NULL;
|
|
- } else {
|
|
- struct loopback_pcm *dpcm = substream->runtime->private_data;
|
|
|
|
- if (cable->ops && cable->ops->close_cable && dpcm)
|
|
- cable->ops->close_cable(dpcm);
|
|
- /* free the cable */
|
|
- loopback->cables[substream->number][dev] = NULL;
|
|
- kfree(cable);
|
|
+ scoped_guard(spinlock_irq, &cable->lock) {
|
|
+ cable->streams[substream->stream] = NULL;
|
|
+ other_alive = cable->streams[!substream->stream];
|
|
}
|
|
+
|
|
+ /* Pair with the stop_count increment in loopback_check_format(). */
|
|
+ wait_event(cable->stop_wait, !atomic_read(&cable->stop_count));
|
|
+ if (other_alive)
|
|
+ return;
|
|
+
|
|
+ dpcm = substream->runtime->private_data;
|
|
+ if (cable->ops && cable->ops->close_cable && dpcm)
|
|
+ cable->ops->close_cable(dpcm);
|
|
+ /* free the cable */
|
|
+ loopback->cables[substream->number][dev] = NULL;
|
|
+ kfree(cable);
|
|
}
|
|
|
|
static int loopback_jiffies_timer_open(struct loopback_pcm *dpcm)
|
|
@@ -1260,6 +1275,8 @@ static int loopback_open(struct snd_pcm_substream *substream)
|
|
goto unlock;
|
|
}
|
|
spin_lock_init(&cable->lock);
|
|
+ atomic_set(&cable->stop_count, 0);
|
|
+ init_waitqueue_head(&cable->stop_wait);
|
|
cable->hw = loopback_pcm_hardware;
|
|
if (loopback->timer_source)
|
|
cable->ops = &loopback_snd_timer_ops;
|
|
--
|
|
2.50.1 (Apple Git-155)
|
|
|