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@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 > > 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 :).
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