[PATCH v3 25/46] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg()

[Alexander Potapenko]

If vring doesn't use the DMA API, KMSAN is unable to tell whether the
memory is initialized by hardware. Explicitly call kmsan_handle_dma()
from vring_map_one_sg() in this case to prevent false positives.

Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

---
Link: https://linux-review.googlesource.com/id/I211533ecb86a66624e151551f83ddd749536b3af
---
 drivers/virtio/virtio_ring.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cfb028ca238eb..faecd9e3d6560 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/hrtimer.h>
 #include <linux/dma-mapping.h>
+#include <linux/kmsan-checks.h>
 #include <linux/spinlock.h>
 #include <xen/xen.h>
 
@@ -331,8 +332,15 @@ static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
 				   struct scatterlist *sg,
 				   enum dma_data_direction direction)
 {
-	if (!vq->use_dma_api)
+	if (!vq->use_dma_api) {
+		/*
+		 * If DMA is not used, KMSAN doesn't know that the scatterlist
+		 * is initialized by the hardware. Explicitly check/unpoison it
+		 * depending on the direction.
+		 */
+		kmsan_handle_dma(sg_page(sg), sg->offset, sg->length, direction);
 		return (dma_addr_t)sg_phys(sg);
+	}
 
 	/*
 	 * We can't use dma_map_sg, because we don't use scatterlists in
-- 
2.36.0.rc2.479.g8af0fa9b8e-goog