From: Takashi Iwai <tiwai@xxxxxxx>
This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit d15d662e89fc667b90cd294b0eb45694e33144da ]
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@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
sound/core/seq/seq_clientmgr.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index df524126a336..b9ce5da25938 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1012,7 +1012,7 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
{
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))
@@ -1027,11 +1027,15 @@ static ssize_t snd_seq_write(struct file *file, const char __user *buf,
/* 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);
--
2.14.1