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authorTakashi Iwai <tiwai@suse.de>2018-02-12 15:20:51 +0100
committerTakashi Iwai <tiwai@suse.de>2018-02-14 10:39:08 +0100
commitd15d662e89fc667b90cd294b0eb45694e33144da (patch)
tree301264d814fae494155ae518c42f380666623ef6
parent1dcb1859dd6752131b85c78fb3e440bd1d2cf361 (diff)
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>
-rw-r--r--sound/core/seq/seq_clientmgr.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c
index 60db32785f62..04d4db44fae5 100644
--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1003,7 +1003,7 @@ 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))
@@ -1018,11 +1018,15 @@ 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);