Re: [PATCH net] net: bridge: netlink: do not clear the vlan info dump error

[Eric Dumazet]

Le mar. 27 oct. 2026 à 09:52, Linkui Xiao <xiaolinkui@xxxxxxx> a écrit :
>
> From: Linkui Xiao <xiaolinkui@xxxxxxxxxx>
>
> br_fill_ifinfo() assigns the result of br_fill_vlan_tunnel_info() over
> the result of br_fill_ifvlaninfo() or br_fill_ifvlaninfo_compressed()
> instead of only running the second helper when the first one succeeded.
>
> When the vlan information no longer fits in the skb but the port has no
> vlan mapped to a tunnel dst, br_fill_vlan_tunnel_info() walks the vlan
> list and returns 0 without touching the skb. The -EMSGSIZE is lost,
> br_fill_ifinfo() completes a message whose IFLA_AF_SPEC is truncated,
> and the dump carries on to the next interface instead of stopping, so
> userspace silently sees an incomplete vlan list.
>
> Only fill the tunnel information when the vlan information was filled
> successfully.
>
> This was flagged as a pre-existing issue in the Sashiko review of the
> net-next series, which noted that the VLAN fill result is overwritten
> before it is tested (see the Link tag below).
>
> Fixes: efa5356b0d97 ("bridge: per vlan dst_metadata netlink support")
> Link: https://lore.kernel.org/bridge/ed1de95e-e112-4076-93f0-6f7668e657ad@xxxxxxxxxxxxx/T/#u#5
> Signed-off-by: Linkui Xiao <xiaolinkui@xxxxxxxxxx>

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>