Re: [PATCH net] netdev: fix double-free in netdev_nl_bind_rx_doit()

[Nikolay Aleksandrov <razor@blackwall.org>]

On 06/06/2026 04:21, Jakub Kicinski wrote:
> Sashiko flags that genlmsg_reply() always consumes the skb.
> The error path calls nlmsg_free(rsp) so we can't jump directly
> to it. Let's not unbind, just propagate the error to the user.
> This is the typical way of handling genlmsg_reply() failures.
> They shouldn't happen unless user does something silly like
> calling the kernel with an already-full rcvbuf.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Fixes: 170aafe35cb9 ("netdev: support binding dma-buf to netdevice")
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: bobbyeshleman@gmail.com
> CC: dw@davidwei.uk
> CC: daniel@iogearbox.net
> CC: razor@blackwall.org
> CC: sdf@fomichev.me
> CC: willemb@google.com
> CC: kaiyuanz@google.com
> ---
>   net/core/netdev-genl.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> index b4d48f3672a5..11b0b91683d7 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -1095,8 +1095,6 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
>   	genlmsg_end(rsp, hdr);
>   
>   	err = genlmsg_reply(rsp, info);
> -	if (err)
> -		goto err_unbind;
>   
>   	bitmap_free(rxq_bitmap);
>   
> @@ -1104,7 +1102,7 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
>   
>   	mutex_unlock(&priv->lock);
>   
> -	return 0;
> +	return err < 0 ? err : 0;
>   
>   err_unbind:
>   	net_devmem_unbind_dmabuf(binding);

Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>