[PATCH net] amt: fix size calculation in amt_get_size()

[PATCH net] amt: fix size calculation in amt_get_size()

[Eric Dumazet]

amt_get_size() incorrectly used sizeof(struct iphdr) for the sizes of
IFLA_AMT_DISCOVERY_IP, IFLA_AMT_REMOTE_IP, and IFLA_AMT_LOCAL_IP.
These attributes contain IPv4 addresses (__be32), not full IP headers.

Replace sizeof(struct iphdr) with sizeof(__be32) to avoid over-allocating
netlink message space.

Fixes: b9022b53adad ("amt: add control plane of amt interface")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 drivers/net/amt.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index 724a8163a5142a6835950abb63d80f29417b2654..951dd10e192b7924f9d3f05065a298ddcf8f4b25 100644
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -3301,9 +3301,9 @@ static size_t amt_get_size(const struct net_device *dev)
 	       nla_total_size(sizeof(__u16)) + /* IFLA_AMT_GATEWAY_PORT */
 	       nla_total_size(sizeof(__u32)) + /* IFLA_AMT_LINK */
 	       nla_total_size(sizeof(__u32)) + /* IFLA_MAX_TUNNELS */
-	       nla_total_size(sizeof(struct iphdr)) + /* IFLA_AMT_DISCOVERY_IP */
-	       nla_total_size(sizeof(struct iphdr)) + /* IFLA_AMT_REMOTE_IP */
-	       nla_total_size(sizeof(struct iphdr)); /* IFLA_AMT_LOCAL_IP */
+	       nla_total_size(sizeof(__be32)) + /* IFLA_AMT_DISCOVERY_IP */
+	       nla_total_size(sizeof(__be32)) + /* IFLA_AMT_REMOTE_IP */
+	       nla_total_size(sizeof(__be32)); /* IFLA_AMT_LOCAL_IP */
 }
 
 static int amt_fill_info(struct sk_buff *skb, const struct net_device *dev)
-- 
2.55.0.rc0.799.gd6f94ed593-goog

Re: [PATCH net] amt: fix size calculation in amt_get_size()

[Kuniyuki Iwashima]

On Wed, Jul 1, 2026 at 5:23 AM Eric Dumazet <edumazet@google.com> wrote:
>
> amt_get_size() incorrectly used sizeof(struct iphdr) for the sizes of
> IFLA_AMT_DISCOVERY_IP, IFLA_AMT_REMOTE_IP, and IFLA_AMT_LOCAL_IP.
> These attributes contain IPv4 addresses (__be32), not full IP headers.
>
> Replace sizeof(struct iphdr) with sizeof(__be32) to avoid over-allocating
> netlink message space.
>
> Fixes: b9022b53adad ("amt: add control plane of amt interface")
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH net] amt: fix size calculation in amt_get_size()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Wed,  1 Jul 2026 12:23:29 +0000 you wrote:
> amt_get_size() incorrectly used sizeof(struct iphdr) for the sizes of
> IFLA_AMT_DISCOVERY_IP, IFLA_AMT_REMOTE_IP, and IFLA_AMT_LOCAL_IP.
> These attributes contain IPv4 addresses (__be32), not full IP headers.
> 
> Replace sizeof(struct iphdr) with sizeof(__be32) to avoid over-allocating
> netlink message space.
> 
> [...]

Here is the summary with links:
  - [net] amt: fix size calculation in amt_get_size()
    https://git.kernel.org/netdev/net/c/9e05e91a9a84

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html