FAILED: patch "[PATCH] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN" failed to apply to 6.1-stable tree

FAILED: patch "[PATCH] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN" failed to apply to 6.1-stable tree

[gregkh]

The patch below does not apply to the 6.1-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 <stable@vger.kernel.org>.

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-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x b4e5f04c58a29c499faa85d12952ca9a4faf1cb9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026040856-ploy-antiviral-fecc@gregkh' --subject-prefix 'PATCH 6.1.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 <schalla@marvell.com>
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: 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 ab2108ee206a..c0b9bc5574e2 100644
--- 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));

[PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Sasha Levin]

From: Srujana Challa <schalla@marvell.com>

[ 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: 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>
[ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/virtio_net.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 9ee3465082c5a..0fcd662d15d51 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3796,6 +3796,7 @@ 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;
@@ -3915,14 +3916,13 @@ 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, 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));
-- 
2.53.0

Re: [PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Michael S. Tsirkin]

On Wed, Apr 08, 2026 at 09:43:51AM -0400, Sasha Levin wrote:
> From: Srujana Challa <schalla@marvell.com>
> 
> [ 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: 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>
> [ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]

Does this not make the subject and the commit log misleading?

> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  drivers/net/virtio_net.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 9ee3465082c5a..0fcd662d15d51 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -3796,6 +3796,7 @@ 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;
> @@ -3915,14 +3916,13 @@ 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, 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));
> -- 
> 2.53.0

Re: [PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Sasha Levin]

On Wed, Apr 08, 2026 at 09:54:33AM -0400, Michael S. Tsirkin wrote:
>On Wed, Apr 08, 2026 at 09:43:51AM -0400, Sasha Levin wrote:
>> From: Srujana Challa <schalla@marvell.com>
>>
>> [ 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: 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>
>> [ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
>
>Does this not make the subject and the commit log misleading?

Probably, but changing the commit subject will just create more confusion.

-- 
Thanks,
Sasha

Re: [PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Michael S. Tsirkin]

On Wed, Apr 08, 2026 at 10:15:48AM -0400, Sasha Levin wrote:
> On Wed, Apr 08, 2026 at 09:54:33AM -0400, Michael S. Tsirkin wrote:
> > On Wed, Apr 08, 2026 at 09:43:51AM -0400, Sasha Levin wrote:
> > > From: Srujana Challa <schalla@marvell.com>
> > > 
> > > [ 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: 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>
> > > [ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
> > 
> > Does this not make the subject and the commit log misleading?
> 
> Probably, but changing the commit subject will just create more confusion.
> 
> -- 
> Thanks,
> Sasha

It's not just the subject. The commit log says:

	Also the value 40 is a spec minimum, not a spec maximum.

but the changed patch seems to treat it as a maximum:

+               vi->rss_key_size = min_t(u16, key_sz, VIRTIO_NET_RSS_MAX_KEY_SIZE);


so unless I misread the code, the value is never > 40.


-- 
MST

Re: [PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Sasha Levin]

On Wed, Apr 08, 2026 at 10:20:50AM -0400, Michael S. Tsirkin wrote:
>On Wed, Apr 08, 2026 at 10:15:48AM -0400, Sasha Levin wrote:
>> On Wed, Apr 08, 2026 at 09:54:33AM -0400, Michael S. Tsirkin wrote:
>> > On Wed, Apr 08, 2026 at 09:43:51AM -0400, Sasha Levin wrote:
>> > > From: Srujana Challa <schalla@marvell.com>
>> > >
>> > > [ 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: 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>
>> > > [ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
>> >
>> > Does this not make the subject and the commit log misleading?
>>
>> Probably, but changing the commit subject will just create more confusion.
>>
>> --
>> Thanks,
>> Sasha
>
>It's not just the subject. The commit log says:
>
>	Also the value 40 is a spec minimum, not a spec maximum.
>
>but the changed patch seems to treat it as a maximum:
>
>+               vi->rss_key_size = min_t(u16, key_sz, VIRTIO_NET_RSS_MAX_KEY_SIZE);
>
>
>so unless I misread the code, the value is never > 40.

I tried to explain it here: https://lore.kernel.org/all/adZitVex9UGVyH-V@laps/

-- 
Thanks,
Sasha

Re: [PATCH 6.1.y] virtio_net: clamp rss_max_key_size to NETDEV_RSS_KEY_LEN

[Michael S. Tsirkin]

On Wed, Apr 08, 2026 at 10:24:14AM -0400, Sasha Levin wrote:
> On Wed, Apr 08, 2026 at 10:20:50AM -0400, Michael S. Tsirkin wrote:
> > On Wed, Apr 08, 2026 at 10:15:48AM -0400, Sasha Levin wrote:
> > > On Wed, Apr 08, 2026 at 09:54:33AM -0400, Michael S. Tsirkin wrote:
> > > > On Wed, Apr 08, 2026 at 09:43:51AM -0400, Sasha Levin wrote:
> > > > > From: Srujana Challa <schalla@marvell.com>
> > > > >
> > > > > [ 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: 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>
> > > > > [ changed clamp target from NETDEV_RSS_KEY_LEN to VIRTIO_NET_RSS_MAX_KEY_SIZE ]
> > > >
> > > > Does this not make the subject and the commit log misleading?
> > > 
> > > Probably, but changing the commit subject will just create more confusion.
> > > 
> > > --
> > > Thanks,
> > > Sasha
> > 
> > It's not just the subject. The commit log says:
> > 
> > 	Also the value 40 is a spec minimum, not a spec maximum.
> > 
> > but the changed patch seems to treat it as a maximum:
> > 
> > +               vi->rss_key_size = min_t(u16, key_sz, VIRTIO_NET_RSS_MAX_KEY_SIZE);
> > 
> > 
> > so unless I misread the code, the value is never > 40.
> 
> I tried to explain it here: https://lore.kernel.org/all/adZitVex9UGVyH-V@laps/
> 
> -- 
> Thanks,
> Sasha


OK let us take the discussion there.