netdev - Re: [PATCH bpf-next] bpf: use the proper optlen when doing strncpy in bpf

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Message-ID: <20190122180457.goq4xgtbi5cuxzwz@kafai-mbp.dhcp.thefacebook.com>
Date:   Tue, 22 Jan 2019 18:04:58 +0000
From:   Martin Lau <kafai@...com>
To:     Yafang Shao <laoar.shao@...il.com>, Lawrence Brakmo <brakmo@...com>
CC:     "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "shaoyafang@...iglobal.com" <shaoyafang@...iglobal.com>
Subject: Re: [PATCH bpf-next] bpf: use the proper optlen when doing strncpy in
 bpf_getsockopt()

On Sat, Jan 19, 2019 at 02:20:52PM +0800, Yafang Shao wrote:
> As the last character of optval will be set with 0, so just copying
> (optlen - 1) characters is enough.
I am not sure this optimization is needed but I think it will
make it more consistent with the bpf_setsockopt() above.

Acked-by: Martin KaFai Lau <kafai@...com>

Cc: Lawrence Brakmo <brakmo@...com>

> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
>  net/core/filter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 447dd1b..7a4de22 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4262,7 +4262,7 @@ static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
>  
>  			if (!icsk->icsk_ca_ops || optlen <= 1)
>  				goto err_clear;
> -			strncpy(optval, icsk->icsk_ca_ops->name, optlen);
> +			strncpy(optval, icsk->icsk_ca_ops->name, optlen - 1);
>  			optval[optlen - 1] = 0;
>  			break;
>  		case TCP_SAVED_SYN:
> -- 
> 1.8.3.1
>