diff mbox series

[4.19,4/5] ALSA: pcm: Fix races among concurrent prealloc proc writes

Message ID 20220513080018.1302825-4-ovidiu.panait@windriver.com
State Superseded
Headers show
Series [4.19,1/5] ALSA: pcm: Fix races among concurrent hw_params and hw_free calls | expand

Commit Message

Ovidiu Panait May 13, 2022, 8 a.m. UTC 
From: Takashi Iwai <tiwai@suse.de>

commit 69534c48ba8ce552ce383b3dfdb271ffe51820c3 upstream.

We have no protection against concurrent PCM buffer preallocation
changes via proc files, and it may potentially lead to UAF or some
weird problem.  This patch applies the PCM open_mutex to the proc
write operation for avoiding the racy proc writes and the PCM stream
open (and further operations).

Cc: <stable@vger.kernel.org>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20220322170720.3529-5-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[OP: backport to 4.19: adjusted context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
---
 sound/core/pcm_memory.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/sound/core/pcm_memory.c b/sound/core/pcm_memory.c
index 4b5356a10315..48e5f0091ce4 100644
--- a/sound/core/pcm_memory.c
+++ b/sound/core/pcm_memory.c
@@ -160,19 +160,20 @@  static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 	size_t size;
 	struct snd_dma_buffer new_dmab;
 
+	mutex_lock(&substream->pcm->open_mutex);
 	if (substream->runtime) {
 		buffer->error = -EBUSY;
-		return;
+		goto unlock;
 	}
 	if (!snd_info_get_line(buffer, line, sizeof(line))) {
 		snd_info_get_str(str, line, sizeof(str));
 		size = simple_strtoul(str, NULL, 10) * 1024;
 		if ((size != 0 && size < 8192) || size > substream->dma_max) {
 			buffer->error = -EINVAL;
-			return;
+			goto unlock;
 		}
 		if (substream->dma_buffer.bytes == size)
-			return;
+			goto unlock;
 		memset(&new_dmab, 0, sizeof(new_dmab));
 		new_dmab.dev = substream->dma_buffer.dev;
 		if (size > 0) {
@@ -180,7 +181,7 @@  static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 						substream->dma_buffer.dev.dev,
 						size, &new_dmab) < 0) {
 				buffer->error = -ENOMEM;
-				return;
+				goto unlock;
 			}
 			substream->buffer_bytes_max = size;
 		} else {
@@ -192,6 +193,8 @@  static void snd_pcm_lib_preallocate_proc_write(struct snd_info_entry *entry,
 	} else {
 		buffer->error = -EINVAL;
 	}
+ unlock:
+	mutex_unlock(&substream->pcm->open_mutex);
 }
 
 static inline void preallocate_info_init(struct snd_pcm_substream *substream)