patch 'vhost: fix descriptor chain bounds check in control queue' has been queued to stable release 25.11.1

[Kevin Traynor]

Hi,

FYI, your patch has been queued to stable release 25.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 03/02/26. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable/commit/19837a1661fdabf716a6cf2ef997b1006e0f4cf3

Thanks.

Kevin

---
>From 19837a1661fdabf716a6cf2ef997b1006e0f4cf3 Mon Sep 17 00:00:00 2001
From: Maxime Coquelin <maxime.coquelin at redhat.com>
Date: Wed, 14 Jan 2026 16:34:44 +0100
Subject: [PATCH] vhost: fix descriptor chain bounds check in control queue

[ upstream commit 6ec17781346e0fe4b566b6bf8f79be71f87c10e4 ]

The virtio_net_ctrl_pop() function traverses descriptor chains from
guest-controlled memory without validating that the descriptor index
stays within bounds and without a counter to prevent infinite loops
from circular chains.

A malicious guest could craft descriptors with a next field pointing
out of bounds causing memory corruption, or create circular descriptor
chains causing an infinite loop and denial of service.

Add bounds checking and a loop counter to both descriptor chain
traversal loops, similar to the existing protection in virtio_net.c
fill_vec_buf_split().

Fixes: 474f4d7840ad ("vhost: add control virtqueue")

Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
Reviewed-by: David Marchand <david.marchand at redhat.com>
Reviewed-by: Chenbo Xia <chenbox at nvidia.com>
---
 lib/vhost/virtio_net_ctrl.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/vhost/virtio_net_ctrl.c b/lib/vhost/virtio_net_ctrl.c
index 603a8db728..b059fe1f02 100644
--- a/lib/vhost/virtio_net_ctrl.c
+++ b/lib/vhost/virtio_net_ctrl.c
@@ -29,5 +29,5 @@ virtio_net_ctrl_pop(struct virtio_net *dev, struct vhost_virtqueue *cvq,
 	__rte_requires_shared_capability(&cvq->iotlb_lock)
 {
-	uint16_t avail_idx, desc_idx, n_descs = 0;
+	uint16_t avail_idx, desc_idx, n_descs = 0, nr_descs, cnt = 0;
 	uint64_t desc_len, desc_addr, desc_iova, data_len = 0;
 	uint8_t *ctrl_req;
@@ -60,10 +60,17 @@ virtio_net_ctrl_pop(struct virtio_net *dev, struct vhost_virtqueue *cvq,
 		}
 
+		nr_descs = desc_len / sizeof(struct vring_desc);
 		desc_idx = 0;
 	} else {
 		descs = cvq->desc;
+		nr_descs = cvq->size;
 	}
 
 	while (1) {
+		if (unlikely(desc_idx >= nr_descs || cnt++ >= nr_descs)) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR, "Invalid ctrl descriptor chain");
+			goto err;
+		}
+
 		desc_len = descs[desc_idx].len;
 		desc_iova = descs[desc_idx].addr;
@@ -143,10 +150,21 @@ virtio_net_ctrl_pop(struct virtio_net *dev, struct vhost_virtqueue *cvq,
 		}
 
+		nr_descs = desc_len / sizeof(struct vring_desc);
 		desc_idx = 0;
 	} else {
 		descs = cvq->desc;
+		nr_descs = cvq->size;
 	}
 
-	while (!(descs[desc_idx].flags & VRING_DESC_F_WRITE)) {
+	cnt = 0;
+	while (1) {
+		if (unlikely(desc_idx >= nr_descs || cnt++ >= nr_descs)) {
+			VHOST_CONFIG_LOG(dev->ifname, ERR, "Invalid ctrl descriptor chain");
+			goto free_err;
+		}
+
+		if (descs[desc_idx].flags & VRING_DESC_F_WRITE)
+			break;
+
 		desc_len = descs[desc_idx].len;
 		desc_iova = descs[desc_idx].addr;
-- 
2.53.0

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2026-02-26 10:16:49.039184979 +0000
+++ 0049-vhost-fix-descriptor-chain-bounds-check-in-control-q.patch	2026-02-26 10:16:46.965349108 +0000
@@ -1 +1 @@
-From 6ec17781346e0fe4b566b6bf8f79be71f87c10e4 Mon Sep 17 00:00:00 2001
+From 19837a1661fdabf716a6cf2ef997b1006e0f4cf3 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 6ec17781346e0fe4b566b6bf8f79be71f87c10e4 ]
+
@@ -20 +21,0 @@
-Cc: stable at dpdk.org