ALSA: seq: Fix racy pool initializations
ALSA sequencer core initializes the event pool on demand by invoking
snd_seq_pool_init() when the first write happens and the pool is
empty. Meanwhile user can reset the pool size manually via ioctl
concurrently, and this may lead to UAF or out-of-bound accesses since
the function tries to vmalloc / vfree the buffer.
A simple fix is to just wrap the snd_seq_pool_init() call with the
recently introduced client->ioctl_mutex; as the calls for
snd_seq_pool_init() from other side are always protected with this
mutex, we can avoid the race.
Reported-by: 范龙飞 <long7573@126.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 60db327..04d4db4 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1003,7 +1003,7 @@
{
struct snd_seq_client *client = file->private_data;
int written = 0, len;
- int err = -EINVAL;
+ int err;
struct snd_seq_event event;
if (!(snd_seq_file_flags(file) & SNDRV_SEQ_LFLG_OUTPUT))
@@ -1018,11 +1018,15 @@
/* allocate the pool now if the pool is not allocated yet */
if (client->pool->size > 0 && !snd_seq_write_pool_allocated(client)) {
- if (snd_seq_pool_init(client->pool) < 0)
+ mutex_lock(&client->ioctl_mutex);
+ err = snd_seq_pool_init(client->pool);
+ mutex_unlock(&client->ioctl_mutex);
+ if (err < 0)
return -ENOMEM;
}
/* only process whole events */
+ err = -EINVAL;
while (count >= sizeof(struct snd_seq_event)) {
/* Read in the event header from the user */
len = sizeof(event);
