On Fri, Jun 10, 2022 at 10:51 PM Michael S. Tsirkin <[email protected]> wrote: > > On Fri, Jun 10, 2022 at 06:33:14PM +0800, huangjie.albert wrote: > > ksoftirqd may consume the packet and it will call: > > virtnet_poll > > -->virtnet_receive > > -->virtqueue_get_buf_ctx > > -->virtqueue_get_buf_ctx_packed > > and in virtqueue_get_buf_ctx_packed: > > > > vq->last_used_idx += vq->packed.desc_state[id].num; > > if (unlikely(vq->last_used_idx >= vq->packed.vring.num)) { > > vq->last_used_idx -= vq->packed.vring.num; > > vq->packed.used_wrap_counter ^= 1; > > } > > > > if at the same time, there comes a vring interrupt，in vring_interrupt: > > we will call: > > vring_interrupt > > -->more_used > > -->more_used_packed > > -->is_used_desc_packed > > in is_used_desc_packed, the last_used_idx maybe >= vq->packed.vring.num. > > so this could case a memory out of bounds bug. > > > > this patch is to fix this. > > > > Signed-off-by: huangjie.albert <[email protected]> > > > This pattern was always iffy, but I don't think the patch > improves the situation much. last_used_idx and vq->packed.used_wrap_counter > can still get out of sync. > > Maybe refactor code to keep everything in vq->last_used_idx? > > Jason what is your take?
I think we can do this since 16bit/32bit operations are guaranteed to be atomic. Thanks > > > > > > > --- > > drivers/virtio/virtio_ring.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index 13a7348cedff..d2abbb3a8187 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -1397,6 +1397,9 @@ static inline bool is_used_desc_packed(const struct > > vring_virtqueue *vq, > > bool avail, used; > > u16 flags; > > > > + if (idx >= vq->packed.vring.num) > > + return false; > > + > > flags = le16_to_cpu(vq->packed.vring.desc[idx].flags); > > avail = !!(flags & (1 << VRING_PACKED_DESC_F_AVAIL)); > > used = !!(flags & (1 << VRING_PACKED_DESC_F_USED)); > > -- > > 2.27.0 > _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
