netdev - RE: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated

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Date:   Fri, 18 Aug 2017 09:19:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Phil Sutter' <phil@....cc>,
        Stephen Hemminger <stephen@...workplumber.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is
 NULL-terminated

From: Phil Sutter
> Sent: 17 August 2017 18:09
> To: Stephen Hemminger
> Cc: netdev@...r.kernel.org
> Subject: [iproute PATCH v2 1/7] ipntable: Make sure filter.name is NULL-terminated
> 
> Signed-off-by: Phil Sutter <phil@....cc>
> ---
>  ip/ipntable.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/ip/ipntable.c b/ip/ipntable.c
> index 879626ee4f491..7be1f04d33d90 100644
> --- a/ip/ipntable.c
> +++ b/ip/ipntable.c
> @@ -633,7 +633,8 @@ static int ipntable_show(int argc, char **argv)
>  		} else if (strcmp(*argv, "name") == 0) {
>  			NEXT_ARG();
> 
> -			strncpy(filter.name, *argv, sizeof(filter.name));
> +			strncpy(filter.name, *argv, sizeof(filter.name) - 1);
> +			filter.name[sizeof(filter.name) - 1] = '\0';

Why not check for overflow instead?
			if (filter.name[sizeof(filter.name) - 1])
				usage("filer name too long");

	David