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authorTakashi Iwai <tiwai@suse.de>2017-02-08 12:35:39 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-14 15:25:41 -0800
commit5024b2fb8e49091044e450a0548979bb711588d6 (patch)
treeef24bbe8e0fa498264157ade3c800860a609ef56 /sound
parent2e0feb524caccbe9c061997f63b97e4f695e816e (diff)
downloadlinux-aarch64-5024b2fb8e49091044e450a0548979bb711588d6.tar.gz
ALSA: seq: Fix race at creating a queue
commit 4842e98f26dd80be3623c4714a244ba52ea096a8 upstream. When a sequencer queue is created in snd_seq_queue_alloc(),it adds the new queue element to the public list before referencing it. Thus the queue might be deleted before the call of snd_seq_queue_use(), and it results in the use-after-free error, as spotted by syzkaller. The fix is to reference the queue object at the right time. Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/seq/seq_queue.c33
1 files changed, 20 insertions, 13 deletions
diff --git a/sound/core/seq/seq_queue.c b/sound/core/seq/seq_queue.c
index 0bec02e89d51..450c5187eecb 100644
--- a/sound/core/seq/seq_queue.c
+++ b/sound/core/seq/seq_queue.c
@@ -181,6 +181,8 @@ void __exit snd_seq_queues_delete(void)
}
}
+static void queue_use(struct snd_seq_queue *queue, int client, int use);
+
/* allocate a new queue -
* return queue index value or negative value for error
*/
@@ -192,11 +194,11 @@ int snd_seq_queue_alloc(int client, int locked, unsigned int info_flags)
if (q == NULL)
return -ENOMEM;
q->info_flags = info_flags;
+ queue_use(q, client, 1);
if (queue_list_add(q) < 0) {
queue_delete(q);
return -ENOMEM;
}
- snd_seq_queue_use(q->queue, client, 1); /* use this queue */
return q->queue;
}
@@ -502,19 +504,9 @@ int snd_seq_queue_timer_set_tempo(int queueid, int client,
return result;
}
-
-/* use or unuse this queue -
- * if it is the first client, starts the timer.
- * if it is not longer used by any clients, stop the timer.
- */
-int snd_seq_queue_use(int queueid, int client, int use)
+/* use or unuse this queue */
+static void queue_use(struct snd_seq_queue *queue, int client, int use)
{
- struct snd_seq_queue *queue;
-
- queue = queueptr(queueid);
- if (queue == NULL)
- return -EINVAL;
- mutex_lock(&queue->timer_mutex);
if (use) {
if (!test_and_set_bit(client, queue->clients_bitmap))
queue->clients++;
@@ -529,6 +521,21 @@ int snd_seq_queue_use(int queueid, int client, int use)
} else {
snd_seq_timer_close(queue);
}
+}
+
+/* use or unuse this queue -
+ * if it is the first client, starts the timer.
+ * if it is not longer used by any clients, stop the timer.
+ */
+int snd_seq_queue_use(int queueid, int client, int use)
+{
+ struct snd_seq_queue *queue;
+
+ queue = queueptr(queueid);
+ if (queue == NULL)
+ return -EINVAL;
+ mutex_lock(&queue->timer_mutex);
+ queue_use(queue, client, use);
mutex_unlock(&queue->timer_mutex);
queuefree(queue);
return 0;