[PULL,16/63] virtio-snd: add max size bounds check in input cb

Commit Message

Michael S. Tsirkin July 22, 2024, 12:17 a.m. UTC

From: Manos Pitsidianakis <[e-mail]>

When reading input audio in the virtio-snd input callback,
virtio_snd_pcm_in_cb(), we do not check whether the iov can actually fit
the data buffer. This is because we use the buffer->size field as a
total-so-far accumulator instead of byte-size-left like in TX buffers.

This triggers an out of bounds write if the size of the virtio queue
element is equal to virtio_snd_pcm_status, which makes the available
space for audio data zero. This commit adds a check for reaching the
maximum buffer size before attempting any writes.

Reported-by: Zheyu Ma <[e-mail]>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2427
Signed-off-by: Manos Pitsidianakis <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Reviewed-by: Michael S. Tsirkin <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>
---
 hw/audio/virtio-snd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Patch

diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
index 5993f4f040..e6432ac959 100644
--- a/hw/audio/virtio-snd.c
+++ b/hw/audio/virtio-snd.c
@@ -1261,7 +1261,7 @@  static void virtio_snd_pcm_in_cb(void *data, int available)
 {
     VirtIOSoundPCMStream *stream = data;
     VirtIOSoundPCMBuffer *buffer;
-    size_t size;
+    size_t size, max_size;
 
     WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
         while (!QSIMPLEQ_EMPTY(&stream->queue)) {
@@ -1275,7 +1275,12 @@  static void virtio_snd_pcm_in_cb(void *data, int available)
                 continue;
             }
 
+            max_size = iov_size(buffer->elem->in_sg, buffer->elem->in_num);
             for (;;) {
+                if (buffer->size >= max_size) {
+                    return_rx_buffer(stream, buffer);
+                    break;
+                }
                 size = AUD_read(stream->voice.in,
                         buffer->data + buffer->size,
                         MIN(available, (stream->params.period_bytes -