> Update ip_tunnel_encap_setup() to use WRITE_ONCE() when writing
> to encap fields (type, sport, dport, flags) and hlen fields.
> This ensures that concurrent lockless readers (like fill_info)
> do not see torn writes.
> 
> Also remove the unsafe memset() on t->encap which could cause
> concurrent readers to transiently see zeroed fields.
> Removing it also fixes a bug where t->encap was left cleared
> even if ip_encap_hlen() failed, resulting in partial configuration.
> 
> Fixes: 56328486539d ("net: Changes to ip_tunnel to support foo-over-udp encapsulation")
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Acked-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

> ---
>  net/ipv4/ip_tunnel.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
> index e6bcf01411d0bcd12cc9a88e449d9283c4a83c64..13b5e35e8790b13ed4c87f28d46aa2bafc9ad72c 100644
> --- a/net/ipv4/ip_tunnel.c
> +++ b/net/ipv4/ip_tunnel.c
> @@ -491,19 +491,17 @@ int ip_tunnel_encap_setup(struct ip_tunnel *t,
>  {
>  	int hlen;
>  
> -	memset(&t->encap, 0, sizeof(t->encap));
> -
>  	hlen = ip_encap_hlen(ipencap);
>  	if (hlen < 0)
>  		return hlen;
>  
> -	t->encap.type = ipencap->type;
> -	t->encap.sport = ipencap->sport;
> -	t->encap.dport = ipencap->dport;
> -	t->encap.flags = ipencap->flags;
> +	WRITE_ONCE(t->encap.type, ipencap->type);
> +	WRITE_ONCE(t->encap.sport, ipencap->sport);
> +	WRITE_ONCE(t->encap.dport, ipencap->dport);
> +	WRITE_ONCE(t->encap.flags, ipencap->flags);
>  
> -	t->encap_hlen = hlen;
> -	t->hlen = t->encap_hlen + t->tun_hlen;
> +	WRITE_ONCE(t->encap_hlen, hlen);
> +	WRITE_ONCE(t->hlen, hlen + t->tun_hlen);
>  
>  	return 0;
>  }
> -- 
> 2.55.0.979.g7e5102b832-goog
>