From 56a588dad8d085a89b24fe2103bd623d4260e02d Mon Sep 17 00:00:00 2001
From: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Date: Mon, 8 Jul 2024 10:09:49 +0300
Subject: [PATCH] virtio-snd: add max size bounds check in input
 cb(CVE-2024-7730)
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cherry-pick from 98e77e3dd8dd6e7aa9a7dffa60f49c8c8a49d4e3

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 <zheyuma97@gmail.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2427
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-Id: <virtio-snd-fuzz-2427-fix-v1-manos.pitsidianakis@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/audio/virtio-snd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/audio/virtio-snd.c b/hw/audio/virtio-snd.c
index 137fa77a01..15986af41e 100644
--- a/hw/audio/virtio-snd.c
+++ b/hw/audio/virtio-snd.c
@@ -1274,7 +1274,7 @@ 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)) {
@@ -1288,7 +1288,12 @@ 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 -
-- 
2.41.0.windows.1