commit ab613b56a1ac4883e12faec71d3eec9c5c44e4f0
author Alexandre Courbot <acourbot@chromium.org> Mon Oct 17 13:10:22 2022 +0900
committer crosvm LUCI <crosvm-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Oct 17 04:31:17 2022 +0000
tree ae2e448add41308d47e73d70468787d9ba5a15e2
parent 894670a919d49a826c5c70fae386569819371067

video: decoder: vda: use wrapping multiplication for timestamp

When decoding using libvda, the frame timestamp is truncated to 32-bits
and needs to be restored to its original value. This is done by doing a
multiplication with the truncation factor. However, if libvda gives us
an invalid timestamp, the multiplication can overflow and cause the
video device process to panic. Avoid this by switching to a wrapping
multiplication - the passed timestamp will still be invalid, but the
decoder device will signal an error instead of crashing.

BUG=None
TEST=cargo build --features "video-decoder,libvda"

Change-Id: Iabe683a997e0e9dea8c2bea53ef520f53868e590
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3958881
Reviewed-by: David Stevens <stevensd@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>

devices/src/virtio/video/decoder/backend/vda.rs

diff --git a/devices/src/virtio/video/decoder/backend/vda.rs b/devices/src/virtio/video/decoder/backend/vda.rs
index 463ce07..22cdc7b 100644
--- a/devices/src/virtio/video/decoder/backend/vda.rs
+++ b/devices/src/virtio/video/decoder/backend/vda.rs
@@ -108,7 +108,7 @@
             } => DecoderEvent::PictureReady {
                 picture_buffer_id: buffer_id,
                 // Restore the truncated timestamp to its original value (hopefully).
-                timestamp: bitstream_id as u64 * TIMESTAMP_TRUNCATE_FACTOR,
+                timestamp: TIMESTAMP_TRUNCATE_FACTOR.wrapping_mul(bitstream_id as u64),
                 visible_rect: Rect {
                     left,
                     top,