The struct virtio_blk_config seg_max value is read from the device and
incremented by 2 to account for the request header and status byte
descriptors added by the driver.
In preparation for supporting untrusted virtio-blk devices, protect
against integer overflow and limit the value to a safe maximum.
Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
---
v2:
* Limit to a virtio-specific value instead of using SG_MAX_SEGMENTS
[Christoph]
---
drivers/block/virtio_blk.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b9fa3ef5b57c..1635d4289202 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -21,6 +21,9 @@
#define VQ_NAME_LEN 16
#define MAX_DISCARD_SEGMENTS 256u
+/* The maximum number of sg elements that fit into a virtqueue */
+#define VIRTIO_BLK_MAX_SG_ELEMS 32768
+
static int major;
static DEFINE_IDA(vd_index_ida);
@@ -728,7 +731,10 @@ static int virtblk_probe(struct virtio_device *vdev)
if (err || !sg_elems)
sg_elems = 1;
- /* We need an extra sg elements at head and tail. */
+ /* Prevent integer overflows and honor max vq size */
+ sg_elems = min_t(u32, sg_elems, VIRTIO_BLK_MAX_SG_ELEMS - 2);
+
+ /* We need extra sg elements at head and tail. */
sg_elems += 2;
vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
if (!vblk) {
--
2.31.1
