Commit 63947b34 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi Committed by Michael S. Tsirkin
Browse files

virtio-blk: limit seg_max to a safe value 



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: default avatarStefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20210524154020.98195-1-stefanha@redhat.com


Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 7a43ce37

drivers/block/virtio_blk.c

+7 −1
Original line number Diff line number Diff line
@@ -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);
@@ -721,7 +724,10 @@ 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) {