[v2,2/2] hw/display: check frame buffer can hold blob

Commit Message

Alex Bennée Nov. 11, 2024, 11 p.m. UTC

Coverity reports (CID 1564769, 1564770) that we potentially overflow
by doing some 32x32 multiplies for something that ends up in a 64 bit
value. Fix this by first using stride for all lines and casting input
to uint64_t to ensure a 64 bit multiply is used.

Signed-off-by: Alex Bennée <[e-mail]>
Cc: Dmitry Osipenko <[e-mail]>

---
v2
  - just use stride * height
  - tweak comment
---
 include/hw/virtio/virtio-gpu.h | 2 +-
 hw/display/virtio-gpu.c        | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

Patch

diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
index 924eb8737e..8c977beebd 100644
--- a/include/hw/virtio/virtio-gpu.h
+++ b/include/hw/virtio/virtio-gpu.h
@@ -340,7 +340,7 @@  void virtio_gpu_update_cursor_data(VirtIOGPU *g,
  * blob_size: size of scanout blob data
  *
  * This will check we have enough space for the frame taking into
- * account that stride for all but the last line.
+ * account that stride.
  *
  * Returns true on success, otherwise logs guest error and returns false
  */
diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
index e7ca8fd1cf..7d22d03bbf 100644
--- a/hw/display/virtio-gpu.c
+++ b/hw/display/virtio-gpu.c
@@ -742,8 +742,7 @@  bool virtio_gpu_scanout_blob_to_fb(struct virtio_gpu_framebuffer *fb,
     fb->offset = ss->offsets[0] + ss->r.x * fb->bytes_pp + ss->r.y * fb->stride;
 
     fbend = fb->offset;
-    fbend += fb->stride * (ss->r.height - 1);
-    fbend += fb->bytes_pp * ss->r.width;
+    fbend += (uint64_t) fb->stride * ss->r.height;
 
     if (fbend > blob_size) {
         qemu_log_mask(LOG_GUEST_ERROR,