FAILED: patch "[PATCH] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN" failed to apply to 6.12-stable tree

PATCH In review [email protected] 4 participants 8 messages Apr 8

Subsystems (3)

Network drivers Stable branch virtio net driver

lore

Share & tools

lore

[email protected]

author maintainer

2026-04-08 06:59 UTC #0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x b4e5f04c58a29c499faa85d12952ca9a4faf1cb9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026040855-hatless-marbled-c4ed@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b4e5f04c58a29c499faa85d12952ca9a4faf1cb9 Mon Sep 17 00:00:00 2001
From: Srujana Challa <[email protected]>
Date: Thu, 26 Mar 2026 19:53:44 +0530
Subject: [PATCH] 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 [email protected]

Signed-off-by Srujana Challa <[email protected]>

Acked-by Michael S. Tsirkin <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Jakub Kicinski <[email protected]>

drivers/net/virtio_net.c +9 ~~-11~~

index ab2108ee206a..c0b9bc5574e2 100644
@@ -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));

Sasha Levin

maintainer

2026-04-08 13:19 UTC #1 lore raw

PATCH 1/1 virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

From: Srujana Challa <[email protected]>

[ 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.

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 [email protected]

Signed-off-by Srujana Challa <[email protected]>

Acked-by Michael S. Tsirkin <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Jakub Kicinski <[email protected]>

[ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]

Signed-off-by Sasha Levin <[email protected]>

---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

drivers/net/virtio_net.c +8 -8

index 5c83983f0eb3f..5a31ccdae2e22 100644
@@ -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));

Signature · 1 line

2.53.0

Srujana Challa

2026-04-08 13:50 UTC #2 lore raw

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

Quoted 74 lines

From: Srujana Challa <[email protected]>
[ 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 [email protected]
Signed-off-by Srujana Challa <[email protected]>
Acked-by Michael S. Tsirkin <[email protected]>
Link https://urldefense.proofpoint.com/v2/url?u=https-
3A__patch.msgid.link_20260326142344.1171317-2D1-2Dschalla- 40marvell.com&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFp ANhTWdwQzjT1Jpf7veC5263T47JVpnc&m=0XuKVXgk9_1LUIZHeqL0znGhAh x5KvAOLvrCl-orVeQSt__4o6Djr-79rwCl6KNp&s=cfQpAcZTTE7nTYku- MVkfip0xUJoBBw4ikqm9iEdgcc&e=
Signed-off-by Jakub Kicinski <[email protected]> [ changed clamp target from
NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
drivers/net/virtio_net.c index renamed from drivers/net/virtio_net.c +0 -0
5c83983f0eb3f..5a31ccdae2e22 100644
drivers/net/virtio_net.c +5 -8
@@ -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);
drivers/net/virtio_net.c +3 -0
+		if (key_sz > vi->rss_key_size)
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u exceeds driver limit
%u, clamping\n",
drivers/net/virtio_net.c +1 -0
+				 key_sz, vi->rss_key_size);
 
 		vi->rss_hash_types_supported =
 		    virtio_cread32(vdev, offsetof(struct virtio_net_config,

Quoted 3 lines

supported_hash_types));
--
2.53.0

We used NETDEV_RSS_KEY_LEN intentionally for clamping. rss_max_key_size is the maximum supported by the device, while 40 is a spec minimum, not a maximum.
Clamping to VIRTIO_NET_RSS_MAX_KEY_SIZE would unnecessarily limit valid devices(for example devices advertising 48/52 bytes) and could reintroduce the original issue.

Could you please share the reason for changing the clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE?

Thanks!

Sasha Levin

maintainer

2026-04-08 14:14 UTC #3 lore raw

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

Quoted 85 lines · Srujana Challa

Quoted 74 lines
From: Srujana Challa <[email protected]>
[ 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 [email protected]
Signed-off-by Srujana Challa <[email protected]>
Acked-by Michael S. Tsirkin <[email protected]>
Link https://urldefense.proofpoint.com/v2/url?u=https-
3A__patch.msgid.link_20260326142344.1171317-2D1-2Dschalla- 40marvell.com&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFp ANhTWdwQzjT1Jpf7veC5263T47JVpnc&m=0XuKVXgk9_1LUIZHeqL0znGhAh x5KvAOLvrCl-orVeQSt__4o6Djr-79rwCl6KNp&s=cfQpAcZTTE7nTYku- MVkfip0xUJoBBw4ikqm9iEdgcc&e=
Signed-off-by Jakub Kicinski <[email protected]> [ changed clamp target from
NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
drivers/net/virtio_net.c index renamed from drivers/net/virtio_net.c +0 -0
5c83983f0eb3f..5a31ccdae2e22 100644
drivers/net/virtio_net.c +5 -8
@@ -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);
drivers/net/virtio_net.c +3 -0
+		if (key_sz > vi->rss_key_size)
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u exceeds driver limit
%u, clamping\n",
drivers/net/virtio_net.c +1 -0
+				 key_sz, vi->rss_key_size);
 
 		vi->rss_hash_types_supported =
 		    virtio_cread32(vdev, offsetof(struct virtio_net_config,
Quoted 3 lines
supported_hash_types));
--
2.53.0
We used NETDEV_RSS_KEY_LEN intentionally for clamping. rss_max_key_size is the maximum supported by the device, while 40 is a spec minimum, not a maximum.
Clamping to VIRTIO_NET_RSS_MAX_KEY_SIZE would unnecessarily limit valid devices(for example devices advertising 48/52 bytes) and could reintroduce the original issue.

Quoted 2 lines

Could you please share the reason for changing the clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE?

Hi Srujana,

In the upstream commit, the key buffer was also enlarged from 40 to 52 bytes as part of the TRAILING_OVERLAP / rss_trailer refactoring:

- u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
+ u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN];

That refactoring isn't present in 6.12, so the key buffer is still u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE] (40 bytes). Clamping to NETDEV_RSS_KEY_LEN
(52) here would allow writing up to 52 bytes into a 40-byte buffer, so the clamp target had to match the actual buffer size in this tree.

Signature · 2 lines

Thanks,
Sasha

Michael S. Tsirkin

maintainer

2026-04-08 14:35 UTC #4 lore raw

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

Quoted 97 lines · Sasha Levin

Quoted 85 lines · Srujana Challa
Quoted 74 lines
From: Srujana Challa <[email protected]>
[ 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 [email protected]
Signed-off-by Srujana Challa <[email protected]>
Acked-by Michael S. Tsirkin <[email protected]>
Link https://urldefense.proofpoint.com/v2/url?u=https-
3A__patch.msgid.link_20260326142344.1171317-2D1-2Dschalla- 40marvell.com&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFp ANhTWdwQzjT1Jpf7veC5263T47JVpnc&m=0XuKVXgk9_1LUIZHeqL0znGhAh x5KvAOLvrCl-orVeQSt__4o6Djr-79rwCl6KNp&s=cfQpAcZTTE7nTYku- MVkfip0xUJoBBw4ikqm9iEdgcc&e=
Signed-off-by Jakub Kicinski <[email protected]> [ changed clamp target from
NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
drivers/net/virtio_net.c index renamed from drivers/net/virtio_net.c +0 -0
5c83983f0eb3f..5a31ccdae2e22 100644
drivers/net/virtio_net.c +5 -8
@@ -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);
drivers/net/virtio_net.c +3 -0
+		if (key_sz > vi->rss_key_size)
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u exceeds driver limit
%u, clamping\n",
drivers/net/virtio_net.c +1 -0
+				 key_sz, vi->rss_key_size);
 
 		vi->rss_hash_types_supported =
 		    virtio_cread32(vdev, offsetof(struct virtio_net_config,
Quoted 3 lines
supported_hash_types));
--
2.53.0
We used NETDEV_RSS_KEY_LEN intentionally for clamping. rss_max_key_size is the maximum supported by the device, while 40 is a spec minimum, not a maximum.
Clamping to VIRTIO_NET_RSS_MAX_KEY_SIZE would unnecessarily limit valid devices(for example devices advertising 48/52 bytes) and could reintroduce the original issue.
Quoted 2 lines
Could you please share the reason for changing the clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE?
Hi Srujana,
In the upstream commit, the key buffer was also enlarged from 40 to 52 bytes as part of the TRAILING_OVERLAP / rss_trailer refactoring:
(quoted diff) +1 -1
-		u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
+		u8 rss_hash_key_data[NETDEV_RSS_KEY_LEN];

Quoted 8 lines

That refactoring isn't present in 6.12, so the key buffer is still u8 key[VIRTIO_NET_RSS_MAX_KEY_SIZE] (40 bytes). Clamping to NETDEV_RSS_KEY_LEN
(52) here would allow writing up to 52 bytes into a 40-byte buffer, so the clamp target had to match the actual buffer size in this tree.
Signature · 2 lines
Thanks,
Sasha

problem is, the commit log now says one thing and the patch does a completely different, and in fact opposite, thing.

Why not pick that dependency then?

Signature · 1 line

MST

Michael S. Tsirkin

maintainer

2026-04-08 14:49 UTC #5 lore raw

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

In reply to Srujana Challa

Quoted 85 lines · Srujana Challa

Quoted 74 lines
From: Srujana Challa <[email protected]>
[ 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 [email protected]
Signed-off-by Srujana Challa <[email protected]>
Acked-by Michael S. Tsirkin <[email protected]>
Link https://urldefense.proofpoint.com/v2/url?u=https-
3A__patch.msgid.link_20260326142344.1171317-2D1-2Dschalla- 40marvell.com&d=DwIDAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=Fj4OoD5hcKFp ANhTWdwQzjT1Jpf7veC5263T47JVpnc&m=0XuKVXgk9_1LUIZHeqL0znGhAh x5KvAOLvrCl-orVeQSt__4o6Djr-79rwCl6KNp&s=cfQpAcZTTE7nTYku- MVkfip0xUJoBBw4ikqm9iEdgcc&e=
Signed-off-by Jakub Kicinski <[email protected]> [ changed clamp target from
NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)
drivers/net/virtio_net.c index renamed from drivers/net/virtio_net.c +0 -0
5c83983f0eb3f..5a31ccdae2e22 100644
drivers/net/virtio_net.c +5 -8
@@ -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);
drivers/net/virtio_net.c +3 -0
+		if (key_sz > vi->rss_key_size)
+			dev_warn(&vdev->dev,
+				 "rss_max_key_size=%u exceeds driver limit
%u, clamping\n",
drivers/net/virtio_net.c +1 -0
+				 key_sz, vi->rss_key_size);
 
 		vi->rss_hash_types_supported =
 		    virtio_cread32(vdev, offsetof(struct virtio_net_config,
Quoted 3 lines
supported_hash_types));
--
2.53.0
We used NETDEV_RSS_KEY_LEN intentionally for clamping. rss_max_key_size is the maximum supported by the device, while 40 is a spec minimum, not a maximum.
Clamping to VIRTIO_NET_RSS_MAX_KEY_SIZE would unnecessarily limit valid devices(for example devices advertising 48/52 bytes) and could reintroduce the original issue.

Quoted 4 lines

Could you please share the reason for changing the clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE?
Thanks!

Srujana,

do you want to do the stable backport yourself?

Signature · 1 line

MST

Sasha Levin

maintainer

2026-04-08 14:56 UTC #6 lore raw

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

Quoted 4 lines · Michael S. Tsirkin

Srujana,
do you want to do the stable backport yourself?

Please feel free to ignore my backport, I was just trying to keep it minimal.

Signature · 2 lines

Thanks,
Sasha

Srujana Challa

2026-04-08 17:01 UTC #7 lore raw

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

Quoted 8 lines · Michael S. Tsirkin

Quoted 4 lines
Srujana,
do you want to do the stable backport yourself?
Please feel free to ignore my backport, I was just trying to keep it minimal.

Thanks for explaining the rationale. Please proceed with your version. I’m not planning to send an additional stable backport on my end. If feasible, please mention in the commit message that the backport clamps to VIRTIO_NET_RSS_MAX_KEY_SIZE since the buffer expansion to NETDEV_RSS_KEY_LEN is not present in this stable tree.

Quoted 3 lines

--
Thanks,
Sasha