[PATCH v3,net] virtio_net: Improve RSS key size validation

[Srujana Challa <schalla@marvell.com>]

Replace hardcoded RSS max key size limit with a type based definition.
Add validation for RSS key size against spec minimum (40 bytes). When
validation fails, gracefully disable RSS features and continue
initialization rather than failing completely.

Cc: stable@vger.kernel.org
Fixes: 3f7d9c1964fc ("virtio_net: Add hash_key_length check")
Signed-off-by: Srujana Challa <schalla@marvell.com>

v3:
- Moved RSS key validation checks to virtnet_validate.
- Add fixes: tag and CC -stable
---
 drivers/net/virtio_net.c | 29 +++++++++++++++++++++--------
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index db88dcaefb20..e61cea50dcab 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -381,7 +381,9 @@ struct receive_queue {
 	struct xdp_buff **xsk_buffs;
 };
 
-#define VIRTIO_NET_RSS_MAX_KEY_SIZE     40
+#define VIRTIO_NET_RSS_MAX_KEY_SIZE \
+	(type_max(((struct virtio_net_config *)0)->rss_max_key_size) + 1)
+#define VIRTIO_NET_RSS_MIN_KEY_SIZE 40
 
 /* Control VQ buffers: protected by the rtnl lock */
 struct control_buf {
@@ -6627,6 +6629,24 @@ static int virtnet_validate(struct virtio_device *vdev)
 		__virtio_clear_bit(vdev, VIRTIO_NET_F_STANDBY);
 	}
 
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS) ||
+	    virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT)) {
+		u8 key_sz = virtio_cread8(vdev,
+					  offsetof(struct virtio_net_config,
+						   rss_max_key_size));
+		/* Spec requires at least 40 bytes */
+		if (key_sz < VIRTIO_NET_RSS_MIN_KEY_SIZE) {
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u is less than spec minimum %u, disabling RSS\n",
+				 key_sz, VIRTIO_NET_RSS_MIN_KEY_SIZE);
+			if (virtio_has_feature(vdev, VIRTIO_NET_F_RSS))
+				__virtio_clear_bit(vdev, VIRTIO_NET_F_RSS);
+			if (virtio_has_feature(vdev, VIRTIO_NET_F_HASH_REPORT))
+				__virtio_clear_bit(vdev,
+						   VIRTIO_NET_F_HASH_REPORT);
+		}
+	}
+
 	return 0;
 }
 
@@ -6839,13 +6859,6 @@ 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;
-		}
-
 		vi->rss_hash_types_supported =
 		    virtio_cread32(vdev, offsetof(struct virtio_net_config, supported_hash_types));
 		vi->rss_hash_types_supported &=
-- 
2.25.1