[dpdk-dev] [PATCH 08/12] vhost: handle virtually non-contiguous buffers in Rx-mrg

[Maxime Coquelin]

This patch enables the handling of buffers non-contiguous in
process virtual address space in the enqueue path when mergeable
buffers are used.

When virtio-net header doesn't fit in a single chunck, it is
computed in a local variable and copied to the buffer chuncks
afterwards.

For packet content, the copy length is limited to the chunck
size, next chuncks VAs being fetched afterward.

This issue has been assigned CVE-2018-1059.

Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 lib/librte_vhost/virtio_net.c | 115 ++++++++++++++++++++++++++++++++----------
 1 file changed, 87 insertions(+), 28 deletions(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 531425792..5fdd4172b 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -638,14 +638,15 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			    uint16_t num_buffers)
 {
 	uint32_t vec_idx = 0;
-	uint64_t desc_addr;
+	uint64_t desc_addr, desc_gaddr;
 	uint32_t mbuf_offset, mbuf_avail;
 	uint32_t desc_offset, desc_avail;
 	uint32_t cpy_len;
-	uint64_t dlen;
+	uint64_t desc_chunck_len;
 	uint64_t hdr_addr, hdr_phys_addr;
 	struct rte_mbuf *hdr_mbuf;
 	struct batch_copy_elem *batch_copy = vq->batch_copy_elems;
+	struct virtio_net_hdr_mrg_rxbuf tmp_hdr, *hdr = NULL;
 	uint16_t copy_nb = vq->batch_copy_nb_elems;
 	int error = 0;
 
@@ -654,26 +655,48 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		goto out;
 	}
 
-	dlen = buf_vec[vec_idx].buf_len;
-	desc_addr = vhost_iova_to_vva(dev, vq, buf_vec[vec_idx].buf_addr,
-						&dlen, VHOST_ACCESS_RW);
-	if (dlen != buf_vec[vec_idx].buf_len ||
-			buf_vec[vec_idx].buf_len < dev->vhost_hlen ||
-			!desc_addr) {
+	desc_chunck_len = buf_vec[vec_idx].buf_len;
+	desc_gaddr = buf_vec[vec_idx].buf_addr;
+	desc_addr = vhost_iova_to_vva(dev, vq,
+					desc_gaddr,
+					&desc_chunck_len,
+					VHOST_ACCESS_RW);
+	if (buf_vec[vec_idx].buf_len < dev->vhost_hlen || !desc_addr) {
 		error = -1;
 		goto out;
 	}
 
 	hdr_mbuf = m;
 	hdr_addr = desc_addr;
-	hdr_phys_addr = buf_vec[vec_idx].buf_addr;
+	if (unlikely(desc_chunck_len < dev->vhost_hlen))
+		hdr = &tmp_hdr;
+	else
+		hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)hdr_addr;
+	hdr_phys_addr = desc_gaddr;
 	rte_prefetch0((void *)(uintptr_t)hdr_addr);
 
 	VHOST_LOG_DEBUG(VHOST_DATA, "(%d) RX: num merge buffers %d\n",
 		dev->vid, num_buffers);
 
 	desc_avail  = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
-	desc_offset = dev->vhost_hlen;
+	if (unlikely(desc_chunck_len < dev->vhost_hlen)) {
+		desc_chunck_len = desc_avail;
+		desc_gaddr += dev->vhost_hlen;
+		desc_addr = vhost_iova_to_vva(dev, vq,
+				desc_gaddr,
+				&desc_chunck_len,
+				VHOST_ACCESS_RW);
+		if (unlikely(!desc_addr)) {
+			error = -1;
+			goto out;
+		}
+
+		desc_offset = 0;
+	} else {
+		desc_offset = dev->vhost_hlen;
+		desc_chunck_len -= dev->vhost_hlen;
+	}
+
 
 	mbuf_avail  = rte_pktmbuf_data_len(m);
 	mbuf_offset = 0;
@@ -681,14 +704,14 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		/* done with current desc buf, get the next one */
 		if (desc_avail == 0) {
 			vec_idx++;
-			dlen = buf_vec[vec_idx].buf_len;
+			desc_chunck_len = buf_vec[vec_idx].buf_len;
+			desc_gaddr = buf_vec[vec_idx].buf_addr;
 			desc_addr =
 				vhost_iova_to_vva(dev, vq,
-					buf_vec[vec_idx].buf_addr,
-					&dlen,
+					desc_gaddr,
+					&desc_chunck_len,
 					VHOST_ACCESS_RW);
-			if (unlikely(!desc_addr ||
-					dlen != buf_vec[vec_idx].buf_len)) {
+			if (unlikely(!desc_addr)) {
 				error = -1;
 				goto out;
 			}
@@ -697,6 +720,17 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			rte_prefetch0((void *)(uintptr_t)desc_addr);
 			desc_offset = 0;
 			desc_avail  = buf_vec[vec_idx].buf_len;
+		} else if (unlikely(desc_chunck_len == 0)) {
+			desc_chunck_len = desc_avail;
+			desc_gaddr += desc_offset;
+			desc_addr = vhost_iova_to_vva(dev, vq,
+					desc_gaddr,
+					&desc_chunck_len, VHOST_ACCESS_RW);
+			if (unlikely(!desc_addr)) {
+				error = -1;
+				goto out;
+			}
+			desc_offset = 0;
 		}
 
 		/* done with current mbuf, get the next one */
@@ -708,30 +742,55 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		}
 
 		if (hdr_addr) {
-			struct virtio_net_hdr_mrg_rxbuf *hdr;
-
-			hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)
-				hdr_addr;
 			virtio_enqueue_offload(hdr_mbuf, &hdr->hdr);
 			ASSIGN_UNLESS_EQUAL(hdr->num_buffers, num_buffers);
 
-			vhost_log_write(dev, hdr_phys_addr, dev->vhost_hlen);
-			PRINT_PACKET(dev, (uintptr_t)hdr_addr,
-				     dev->vhost_hlen, 0);
+			if (unlikely(hdr == &tmp_hdr)) {
+				uint64_t len;
+				uint64_t remain = dev->vhost_hlen;
+				uint64_t src = (uint64_t)(uintptr_t)hdr, dst;
+				uint64_t guest_addr = hdr_phys_addr;
+
+				while (remain) {
+					len = remain;
+					dst = vhost_iova_to_vva(dev, vq,
+							guest_addr, &len,
+							VHOST_ACCESS_RW);
+					if (unlikely(!dst || !len)) {
+						error = -1;
+						goto out;
+					}
+
+					rte_memcpy((void *)(uintptr_t)dst,
+							(void *)(uintptr_t)src,
+							len);
+
+					PRINT_PACKET(dev, (uintptr_t)dst,
+							(uint32_t)len, 0);
+					vhost_log_write(dev, guest_addr, len);
+
+					remain -= len;
+					guest_addr += len;
+					dst += len;
+				}
+			} else {
+				PRINT_PACKET(dev, (uintptr_t)hdr_addr,
+						dev->vhost_hlen, 0);
+				vhost_log_write(dev, hdr_phys_addr,
+						dev->vhost_hlen);
+			}
 
 			hdr_addr = 0;
 		}
 
-		cpy_len = RTE_MIN(desc_avail, mbuf_avail);
+		cpy_len = RTE_MIN(desc_chunck_len, mbuf_avail);
 
 		if (likely(cpy_len > MAX_BATCH_LEN || copy_nb >= vq->size)) {
 			rte_memcpy((void *)((uintptr_t)(desc_addr +
 							desc_offset)),
 				rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
 				cpy_len);
-			vhost_log_write(dev,
-				buf_vec[vec_idx].buf_addr + desc_offset,
-				cpy_len);
+			vhost_log_write(dev, desc_gaddr + desc_offset, cpy_len);
 			PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset),
 				cpy_len, 0);
 		} else {
@@ -739,8 +798,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				(void *)((uintptr_t)(desc_addr + desc_offset));
 			batch_copy[copy_nb].src =
 				rte_pktmbuf_mtod_offset(m, void *, mbuf_offset);
-			batch_copy[copy_nb].log_addr =
-				buf_vec[vec_idx].buf_addr + desc_offset;
+			batch_copy[copy_nb].log_addr = desc_gaddr + desc_offset;
 			batch_copy[copy_nb].len = cpy_len;
 			copy_nb++;
 		}
@@ -749,6 +807,7 @@ copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		mbuf_offset += cpy_len;
 		desc_avail  -= cpy_len;
 		desc_offset += cpy_len;
+		desc_chunck_len -= cpy_len;
 	}
 
 out:
-- 
2.14.3