Blame SOURCES/0002-vhost-fix-header-spanned-across-more-than-two-descri.patch

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From e12d415556994d0901c317f6338ed2961185465f Mon Sep 17 00:00:00 2001
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Message-Id: <e12d415556994d0901c317f6338ed2961185465f.1666780268.git.tredaelli@redhat.com>
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In-Reply-To: <f167022606b5ccca27a627ae599538ce2348ef67.1666780268.git.tredaelli@redhat.com>
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References: <f167022606b5ccca27a627ae599538ce2348ef67.1666780268.git.tredaelli@redhat.com>
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From: Maxime Coquelin <maxime.coquelin@redhat.com>
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Date: Thu, 16 Jun 2022 14:25:07 +0200
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Subject: [PATCH 2/2] vhost: fix header spanned across more than two
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 descriptors
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[ upstream commit dc1516e260a0df272b218392faf6db3cbf45e717 ]
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This patch aims at supporting the unlikely case where a
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Virtio-net header is spanned across more than two
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descriptors.
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CVE-2022-2132
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Fixes: fd68b4739d2c ("vhost: use buffer vectors in dequeue path")
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Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
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Acked-by: Chenbo Xia <chenbo.xia@intel.com>
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Reviewed-by: David Marchand <david.marchand@redhat.com>
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---
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 lib/vhost/virtio_net.c | 41 +++++++++++++----------------------------
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 1 file changed, 13 insertions(+), 28 deletions(-)
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diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
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index 991a7a2bd4..bf4d75b4bd 100644
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--- a/lib/vhost/virtio_net.c
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+++ b/lib/vhost/virtio_net.c
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@@ -2322,25 +2322,22 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
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 	uint32_t buf_avail, buf_offset;
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 	uint64_t buf_addr, buf_len;
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 	uint32_t mbuf_avail, mbuf_offset;
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+	uint32_t hdr_remain = dev->vhost_hlen;
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 	uint32_t cpy_len;
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 	struct rte_mbuf *cur = m, *prev = m;
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 	struct virtio_net_hdr tmp_hdr;
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 	struct virtio_net_hdr *hdr = NULL;
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-	/* A counter to avoid desc dead loop chain */
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-	uint16_t vec_idx = 0;
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+	uint16_t vec_idx;
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 	struct batch_copy_elem *batch_copy = vq->batch_copy_elems;
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 	int error = 0;
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-	buf_addr = buf_vec[vec_idx].buf_addr;
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-	buf_len = buf_vec[vec_idx].buf_len;
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-
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 	/*
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 	 * The caller has checked the descriptors chain is larger than the
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 	 * header size.
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 	 */
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 	if (virtio_net_with_host_offload(dev)) {
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-		if (unlikely(buf_len < sizeof(struct virtio_net_hdr))) {
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+		if (unlikely(buf_vec[0].buf_len < sizeof(struct virtio_net_hdr))) {
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 			/*
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 			 * No luck, the virtio-net header doesn't fit
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 			 * in a contiguous virtual area.
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@@ -2348,34 +2345,22 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
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 			copy_vnet_hdr_from_desc(&tmp_hdr, buf_vec);
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 			hdr = &tmp_hdr;
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 		} else {
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-			hdr = (struct virtio_net_hdr *)((uintptr_t)buf_addr);
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+			hdr = (struct virtio_net_hdr *)((uintptr_t)buf_vec[0].buf_addr);
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 		}
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 	}
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-	/*
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-	 * A virtio driver normally uses at least 2 desc buffers
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-	 * for Tx: the first for storing the header, and others
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-	 * for storing the data.
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-	 */
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-	if (unlikely(buf_len < dev->vhost_hlen)) {
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-		buf_offset = dev->vhost_hlen - buf_len;
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-		vec_idx++;
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-		buf_addr = buf_vec[vec_idx].buf_addr;
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-		buf_len = buf_vec[vec_idx].buf_len;
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-		buf_avail  = buf_len - buf_offset;
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-	} else if (buf_len == dev->vhost_hlen) {
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-		if (unlikely(++vec_idx >= nr_vec))
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-			goto out;
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-		buf_addr = buf_vec[vec_idx].buf_addr;
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-		buf_len = buf_vec[vec_idx].buf_len;
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+	for (vec_idx = 0; vec_idx < nr_vec; vec_idx++) {
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+		if (buf_vec[vec_idx].buf_len > hdr_remain)
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+			break;
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-		buf_offset = 0;
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-		buf_avail = buf_len;
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-	} else {
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-		buf_offset = dev->vhost_hlen;
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-		buf_avail = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
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+		hdr_remain -= buf_vec[vec_idx].buf_len;
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 	}
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+	buf_addr = buf_vec[vec_idx].buf_addr;
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+	buf_len = buf_vec[vec_idx].buf_len;
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+	buf_offset = hdr_remain;
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+	buf_avail = buf_vec[vec_idx].buf_len - hdr_remain;
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+
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 	PRINT_PACKET(dev,
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 			(uintptr_t)(buf_addr + buf_offset),
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 			(uint32_t)buf_avail, 0);
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-- 
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2.37.3
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