From: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>

The amount of bytes to read passed to AUD_read() should never surpass
the maximum available buffer length. Tighten the current amount by
MIN(<amount>, max_size - <existing size>).

Cc: qemu-stable@nongnu.org
Fixes: 98e77e3dd8dd6e7aa9a7dffa60f49c8c8a49d4e3 ("virtio-snd: add max size bounds check in input cb")
Reported-by: DARKNAVY <vr@darknavy.com>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260220-virtio-snd-series-v1-5-207c4f7200a2@linaro.org>
(cherry picked from commit 7994203bb1b83a6604f3ab00fe9598909bb66164)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
index 4ea2d4db95..3653b52d7e 100644
--- a/hw/audio/virtio-snd.c
+++ b/hw/audio/virtio-snd.c
@@ -1240,7 +1240,7 @@ static void virtio_snd_pcm_in_cb(void *data, int available)
 {
     VirtIOSoundPCMStream *stream = data;
     VirtIOSoundPCMBuffer *buffer;
-    size_t size, max_size;
+    size_t size, max_size, to_read;
 
     WITH_QEMU_LOCK_GUARD(&stream->queue_mutex) {
         while (!QSIMPLEQ_EMPTY(&stream->queue)) {
@@ -1266,10 +1266,12 @@ static void virtio_snd_pcm_in_cb(void *data, int available)
                     return_rx_buffer(stream, buffer);
                     break;
                 }
+                to_read = stream->params.period_bytes - buffer->size;
+                to_read = MIN(to_read, available);
+                to_read = MIN(to_read, max_size - buffer->size);
                 size = AUD_read(stream->voice.in,
-                        buffer->data + buffer->size,
-                        MIN(available, (stream->params.period_bytes -
-                                        buffer->size)));
+                                buffer->data + buffer->size,
+                                to_read);
                 if (!size) {
                     available = 0;
                     break;
-- 
2.47.3