[PATCH 6.12.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

Sasha Levin
2026-04-08T13:19:09Z

From: Srujana Challa <schalla@marvell.com>

[ Upstream commit b4e5f04c58a29c499faa85d12952ca9a4faf1cb9 ]

rss_max_key_size in the virtio spec is the maximum key size supported by
the device, not a mandatory size the driver must use. Also the value 40
is a spec minimum, not a spec maximum.

The current code rejects RSS and can fail probe when the device reports a
larger rss_max_key_size than the driver buffer limit. Instead, clamp the
effective key length to min(device rss_max_key_size, NETDEV_RSS_KEY_LEN)
and keep RSS enabled.

This keeps probe working on devices that advertise larger maximum key sizes
while respecting the netdev RSS key buffer size limit.

Fixes: 3f7d9c1964fc ("virtio_net: Add hash_key_length check")
Cc: stable@vger.kernel.org
Signed-off-by: Srujana Challa <schalla@marvell.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20260326142344.1171317-1-schalla@marvell.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/virtio_net.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 5c83983f0eb3f..5a31ccdae2e22 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -6502,6 +6502,7 @@ static int virtnet_probe(struct virtio_device *vdev)
struct virtnet_info *vi;
u16 max_queue_pairs;
int mtu = 0;
+ u16 key_sz;

/* Find if host supports multiqueue/rss virtio_net device */
max_queue_pairs = 1;
@@ -6624,14 +6625,13 @@ static int virtnet_probe(struct virtio_device *vdev)
goto free;

if (vi->has_rss || vi->has_rss_hash_report) {
- vi->rss_key_size =
- virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));
- if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
- dev_err(&vdev->dev, "rss_max_key_size=%u exceeds the limit %u.\n",
- vi->rss_key_size, VIRTIO_NET_RSS_MAX_KEY_SIZE);
- err = -EINVAL;
- goto free;
- }
+ key_sz = virtio_cread8(vdev, offsetof(struct virtio_net_config, rss_max_key_size));
+
+ vi->rss_key_size = min_t(u16, key_sz, VIRTIO_NET_RSS_MAX_KEY_SIZE);
+ if (key_sz > vi->rss_key_size)
+ dev_warn(&vdev->dev,
+ "rss_max_key_size=%u exceeds driver limit %u, clamping\n",
+ key_sz, vi->rss_key_size);

vi->rss_hash_types_supported =
virtio_cread32(vdev, offsetof(struct virtio_net_config, supported_hash_types));
--
2.53.0