Subject: Re: [net-next v1] pfcp: avoid copy warning by simplifing code

From: Michal Swiatkowski <[email-masked]>
Date: Thu, 4 Apr 2024 15:59:12 +0200

On Thu, Apr 04, 2024 at 03:57:21PM +0200, Michal Swiatkowski wrote:
> From Arnd comment:
> "The memcpy() in the ip_tunnel_info_opts_set() causes
> a string.h fortification warning, with at least gcc-13:
> 
>     In function 'fortify_memcpy_chk',
>         inlined from 'ip_tunnel_info_opts_set' at include/net/ip_tunnels.h:619:3,
>         inlined from 'pfcp_encap_recv' at drivers/net/pfcp.c:84:2:
>     include/linux/fortify-string.h:553:25: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
>       553 |                         __write_overflow_field(p_size_field, size);"
> 
> It is a false-positivie caused by ambiguity of the union.
> 
> However, as Arnd noticed, copying here is unescessary. The code can be
> simplified to avoid calling ip_tunnel_info_opts_set(), which is doing
> copying, setting flags and options_len.
> 
> Set correct flags and options_len directly on tun_info.
> 
> Reported-by: Arnd Bergmann <[email-masked]>
> Signed-off-by: Michal Swiatkowski <[email-masked]>
> ---
>  drivers/net/pfcp.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/pfcp.c b/drivers/net/pfcp.c
> index cc5b28c5f99f..69434fd13f96 100644
> --- a/drivers/net/pfcp.c
> +++ b/drivers/net/pfcp.c
> @@ -80,9 +80,8 @@ static int pfcp_encap_recv(struct sock *sk, struct sk_buff *skb)
>  	else
>  		pfcp_node_recv(pfcp, skb, md);
>  
> -	__set_bit(IP_TUNNEL_PFCP_OPT_BIT, flags);
> -	ip_tunnel_info_opts_set(&tun_dst->u.tun_info, md, sizeof(*md),
> -				flags);
> +	__set_bit(IP_TUNNEL_PFCP_OPT_BIT, tun_dst->u.tun_info.key.tun_flags);
> +	tun_dst->u.tun_info.options_len = sizeof(*md);
>  
>  	if (unlikely(iptunnel_pull_header(skb, PFCP_HLEN, skb->protocol,
>  					  !net_eq(sock_net(sk),
> -- 
> 2.42.0
> 

Ehh, sorry, misstype in netdev ccing
CC: [email-masked]