virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

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>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ab2108ee206a91271859c860aa4979947d9bae4d..c0b9bc5574e232683cd9b6378793cb0c88511121 100644 (file)
--- 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;
@@ -486,7 +484,7 @@ 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) ==
@@ -6708,6 +6706,7 @@ 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;
@@ -6842,14 +6841,13 @@ static int virtnet_probe(struct virtio_device *vdev)
        }
 
        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));