Commit b4e5f04c authored by Srujana Challa's avatar Srujana Challa Committed by Jakub Kicinski
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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: 3f7d9c19 ("virtio_net: Add hash_key_length check")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSrujana Challa <schalla@marvell.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Link: https://patch.msgid.link/20260326142344.1171317-1-schalla@marvell.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent d64cb81d

drivers/net/virtio_net.c

+9 −11
Original line number Diff line number Diff line
@@ -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));