Messages in this thread | | | Subject | Re: [RFC PATCH 17/17] virtio_ring: Add validation for used length | From | Jason Wang <> | Date | Tue, 25 May 2021 09:31:33 +0800 |
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在 2021/5/18 上午7:39, Michael S. Tsirkin 写道: > On Mon, May 17, 2021 at 05:08:36PM +0800, Xie Yongji wrote: >> This adds validation for used length (might come >> from an untrusted device) when it will be used by >> virtio device driver. >> >> Signed-off-by: Xie Yongji <xieyongji@bytedance.com> >> --- >> drivers/virtio/virtio_ring.c | 22 +++++++++++++++++++--- >> 1 file changed, 19 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >> index d999a1d6d271..7d4845d06f21 100644 >> --- a/drivers/virtio/virtio_ring.c >> +++ b/drivers/virtio/virtio_ring.c >> @@ -68,11 +68,13 @@ >> struct vring_desc_state_split { >> void *data; /* Data for callback. */ >> struct vring_desc *indir_desc; /* Indirect descriptor, if any. */ >> + u32 in_len; /* Total length of writable buffer */ >> }; >> >> struct vring_desc_state_packed { >> void *data; /* Data for callback. */ >> struct vring_packed_desc *indir_desc; /* Indirect descriptor, if any. */ >> + u32 in_len; /* Total length of writable buffer */ >> u16 num; /* Descriptor list length. */ >> u16 last; /* The last desc state in a list. */ >> }; > > Hmm for packed it's aligned to 64 bit anyway, so we are not making it > any worse. But for split this pushes struct size up by 1/3 increasing > cache pressure.
We can eliminate this by validating through virtio device driver instead of virtio core.
E.g for virtio-net we know the rx buffer size so there's no need to store in twice in the core.
Thanks
> > >> @@ -486,7 +488,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, >> struct vring_virtqueue *vq = to_vvq(_vq); >> struct scatterlist *sg; >> struct vring_desc *desc; >> - unsigned int i, n, avail, descs_used, prev, err_idx; >> + unsigned int i, n, avail, descs_used, prev, err_idx, in_len = 0; >> int head; >> bool indirect; >> >> @@ -570,6 +572,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, >> VRING_DESC_F_NEXT | >> VRING_DESC_F_WRITE, >> indirect); >> + in_len += sg->length; >> } >> } >> /* Last one doesn't continue. */ >> @@ -604,6 +607,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, >> >> /* Store token and indirect buffer state. */ >> vq->split.desc_state[head].data = data; >> + vq->split.desc_state[head].in_len = in_len; >> if (indirect) >> vq->split.desc_state[head].indir_desc = desc; >> else >> @@ -784,6 +788,10 @@ static void *virtqueue_get_buf_ctx_split(struct virtqueue *_vq, >> BAD_RING(vq, "id %u is not a head!\n", i); >> return NULL; >> } >> + if (unlikely(len && vq->split.desc_state[i].in_len < *len)) { >> + BAD_RING(vq, "id %u has invalid length: %u!\n", i, *len); >> + return NULL; >> + } >> >> /* detach_buf_split clears data, so grab it now. */ >> ret = vq->split.desc_state[i].data; >> @@ -1059,7 +1067,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, >> { >> struct vring_packed_desc *desc; >> struct scatterlist *sg; >> - unsigned int i, n, err_idx; >> + unsigned int i, n, err_idx, in_len = 0; >> u16 head, id; >> dma_addr_t addr; >> >> @@ -1084,6 +1092,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, >> if (vring_mapping_error(vq, addr)) >> goto unmap_release; >> >> + in_len += (n < out_sgs) ? 0 : sg->length; >> desc[i].flags = cpu_to_le16(n < out_sgs ? >> 0 : VRING_DESC_F_WRITE); >> desc[i].addr = cpu_to_le64(addr); >> @@ -1141,6 +1150,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq, >> vq->packed.desc_state[id].data = data; >> vq->packed.desc_state[id].indir_desc = desc; >> vq->packed.desc_state[id].last = id; >> + vq->packed.desc_state[id].in_len = in_len; >> >> vq->num_added += 1; >> >> @@ -1173,7 +1183,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, >> struct vring_virtqueue *vq = to_vvq(_vq); >> struct vring_packed_desc *desc; >> struct scatterlist *sg; >> - unsigned int i, n, c, descs_used, err_idx; >> + unsigned int i, n, c, descs_used, err_idx, in_len = 0; >> __le16 head_flags, flags; >> u16 head, id, prev, curr, avail_used_flags; >> >> @@ -1223,6 +1233,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, >> if (vring_mapping_error(vq, addr)) >> goto unmap_release; >> >> + in_len += (n < out_sgs) ? 0 : sg->length; >> flags = cpu_to_le16(vq->packed.avail_used_flags | >> (++c == total_sg ? 0 : VRING_DESC_F_NEXT) | >> (n < out_sgs ? 0 : VRING_DESC_F_WRITE)); >> @@ -1268,6 +1279,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, >> vq->packed.desc_state[id].data = data; >> vq->packed.desc_state[id].indir_desc = ctx; >> vq->packed.desc_state[id].last = prev; >> + vq->packed.desc_state[id].in_len = in_len; >> >> /* >> * A driver MUST NOT make the first descriptor in the list >> @@ -1456,6 +1468,10 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, >> BAD_RING(vq, "id %u is not a head!\n", id); >> return NULL; >> } >> + if (unlikely(len && vq->packed.desc_state[id].in_len < *len)) { >> + BAD_RING(vq, "id %u has invalid length: %u!\n", id, *len); >> + return NULL; >> + } >> >> /* detach_buf_packed clears data, so grab it now. */ >> ret = vq->packed.desc_state[id].data; >> -- >> 2.11.0
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