netdev - RE: [PATCH 4/5] misc: fix compiler warning in ifstat and nstat

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Message-ID: <efb6a29fef0e4ca1845956701f670b4b@AcuMS.aculab.com>
Date:   Mon, 30 Nov 2020 09:18:59 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Stephen Hemminger' <stephen@...workplumber.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 4/5] misc: fix compiler warning in ifstat and nstat

From: Stephen Hemminger
> Sent: 30 November 2020 00:22
> 
> The code here was doing strncpy() in a way that causes gcc 10
> warning about possible string overflow. Just use strlcpy() which
> will null terminate and bound the string as expected.
> 
> This has existed since start of git era so no Fixes tag.
> 
> Signed-off-by: Stephen Hemminger <stephen@...workplumber.org>
> ---
>  misc/ifstat.c | 2 +-
>  misc/nstat.c  | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/misc/ifstat.c b/misc/ifstat.c
> index c05183d79a13..d4a33429dc50 100644
> --- a/misc/ifstat.c
> +++ b/misc/ifstat.c
> @@ -251,7 +251,7 @@ static void load_raw_table(FILE *fp)
>  			buf[strlen(buf)-1] = 0;
>  			if (info_source[0] && strcmp(info_source, buf+1))
>  				source_mismatch = 1;
> -			strncpy(info_source, buf+1, sizeof(info_source)-1);
> +			strlcpy(info_source, buf+1, sizeof(info_source));
>  			continue;

ISTM that once it has done a strlen() it ought to use the length
for the later copy.

I don't seem to have the source file (I'm guessing it isn't in the
normal repo), but is that initial strlen() guaranteed not to return
zero?

	David

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