Re: [PATCH v3 net] vlan: fix skb_under_panic and races when toggling HW VLAN offload

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

On Tue, 11 Aug 2026 08:52:46 +0000 you wrote:
> Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or
> NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(),
> which dynamically changed vlandev->hard_header_len.
> 
> This causes two issues:
> 1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2)
>    read dev->hard_header_len without holding RTNL lock. Mutating
>    hard_header_len dynamically under RTNL creates a data race where upper
>    layers reserve insufficient headroom based on a stale hard_header_len,
>    resulting in skb_under_panic when vlan_dev_hard_header() is called.
> 2. In addition, vlan_transfer_features() updated hard_header_len without
>    updating header_ops, causing a mismatch between allocated headroom
>    and header creation.
> 
> [...]

Here is the summary with links:
  - [v3,net] vlan: fix skb_under_panic and races when toggling HW VLAN offload
    https://git.kernel.org/netdev/net/c/447cbe95ebb9

You are awesome, thank you!
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