linux-kernel - Re: [PATCH] Change judgment len position

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Date:   Wed, 24 Oct 2018 10:10:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     wanghaifine@...il.com
Cc:     edumazet@...gle.com, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Change judgment len position

From: Wang Hai <wanghaifine@...il.com>
Date: Wed, 24 Oct 2018 23:47:29 +0800

> To determine whether len is less than zero, it should be put before 
> the function min_t, because the return value of min_t is not likely 
> to be less than zero.
> 
> Signed-off-by: Wang Hai <wanghaifine@...il.com>
> ---
>  net/ipv4/tcp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 10c624639..49af9fdc3 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3301,11 +3301,11 @@ static int do_tcp_getsockopt(struct sock *sk, int level,
>  	struct net *net = sock_net(sk);
>  	int val, len;
>  
> +	len = min_t(unsigned int, len, sizeof(int));
> +
>  	if (get_user(len, optlen))
>  		return -EFAULT;

You can't be serious?

'len' has no value before the get_user() call.