[PATCH 6.18 235/277] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

Greg Kroah-Hartman
2026-04-08T18:37:26Z

From: Srujana Challa <schalla@marvell.com>

commit b4e5f04c58a29c499faa85d12952ca9a4faf1cb9 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/virtio_net.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -381,8 +381,6 @@ struct receive_queue {
struct xdp_buff **xsk_buffs;
};

-#define VIRTIO_NET_RSS_MAX_KEY_SIZE 40
-
/* Control VQ buffers: protected by the rtnl lock */
struct control_buf {
struct virtio_net_ctrl_hdr hdr;
@@ -495,7 +493,7 @@ struct virtnet_info {

/* Must be last as it ends in a flexible-array member. */
TRAILING_OVERLAP(struct virtio_net_rss_config_trailer, rss_trailer, hash_key_data,
- u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
+ u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN];
);
};
static_assert(offsetof(struct virtnet_info, rss_trailer.hash_key_data) ==
@@ -6794,6 +6792,7 @@ static int virtnet_probe(struct virtio_d
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;
@@ -6929,14 +6928,13 @@ static int virtnet_probe(struct virtio_d
}

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, NETDEV_RSS_KEY_LEN);
+ 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));