Re: [PATCH] ipvs:set sock send/receive buffer correctly

[Eric Dumazet]

On 04/17/2019 02:18 AM, linmiaohe wrote:
> From: Jie Liu <liujie165@xxxxxxxxxx>
> 
> If we set sysctl_wmem_max or sysctl_rmem_max larger than INT_MAX,
> the send/receive buffer of sock will be an negative value. Same as
> when the val is larger than INT_MAX/2.
> 
> Fixes: 1c003b1580e2 ("ipvs: wakeup master thread")
> Reported-by: Qiang Ning <ningqiang1@xxxxxxxxxx>
> Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Signed-off-by: Jie Liu <liujie165@xxxxxxxxxx>
> ---
>  net/netfilter/ipvs/ip_vs_sync.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
> index 2526be6b3d90..c0e4cbed6e74 100644
> --- a/net/netfilter/ipvs/ip_vs_sync.c
> +++ b/net/netfilter/ipvs/ip_vs_sync.c
> @@ -1278,14 +1278,12 @@ static void set_sock_size(struct sock *sk, int mode, int val)
>  	/* setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &val, sizeof(val)); */
>  	lock_sock(sk);
>  	if (mode) {
> -		val = clamp_t(int, val, (SOCK_MIN_SNDBUF + 1) / 2,
> -			      sysctl_wmem_max);
> -		sk->sk_sndbuf = val * 2;
> +		val = min_t(u32, val, sysctl_wmem_max);
> +		sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);

What prevents val * 2 to overflow ? 

Code in sock_setsockopt() looks quite different.

>  		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
>  	} else {
> -		val = clamp_t(int, val, (SOCK_MIN_RCVBUF + 1) / 2,
> -			      sysctl_rmem_max);
> -		sk->sk_rcvbuf = val * 2;
> +		val = min_t(u32, val, sysctl_rmem_max);
> +		sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF);
>  		sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
>  	}
>  	release_sock(sk);
>