| Message ID | 20210524154020.98195-1-stefanha@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] virtio-blk: limit seg_max to a safe value | expand |
On Mon, May 24, 2021 at 04:40:20PM +0100, Stefan Hajnoczi wrote: > 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@redhat.com> Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de>
On Mon, May 24, 2021 at 04:40:20PM +0100, Stefan Hajnoczi wrote: > 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@redhat.com> > --- > 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 32768 is what it says for split queues but for packed queues it says 2^15. So 0x8000 then? > + > 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. */ s/an extra/extra/ > + /* 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 >
On Mon, May 24, 2021 at 04:47:37PM -0400, Michael S. Tsirkin wrote: > On Mon, May 24, 2021 at 04:40:20PM +0100, Stefan Hajnoczi wrote: > > 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@redhat.com> > > --- > > 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 > > 32768 is what it says for split queues but for packed queues > it says 2^15. > > So 0x8000 then? Yes. 2^15 = 0x8000 = 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. */ > > s/an extra/extra/ That line is being removed by this patch :).
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) {
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@redhat.com> --- 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(-)