[PATCH v7 22/43] virtio: kmsan: check/unpoison scatterlist in vring_map_one_sg()

Alexander Potapenko
2022-09-15T15:08:53Z

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@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

---
v4:
-- swap virtio: and kmsan: in the subject

v6:
-- use <linux/kmsan.h> instead of <linux/kmsan-checks.h>

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 4620e9d79dde8..8974c34b40fda 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.h>
#include <linux/spinlock.h>
#include <xen/xen.h>

@@ -352,8 +353,15 @@ 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
--
2.37.2.789.g6183377224-goog