linux-kernel - Re: [PATCH 2/2] string: teach strnstr() to not search past NUL-terminator

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Date:	Mon, 18 Jan 2010 09:47:49 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	André Goddard Rosa <andre.goddard@...il.com>
CC:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	Alex Riesen <raa.lkml@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] string: teach strnstr() to not search past NUL-terminator

André Goddard Rosa wrote:
> As noticed by Alex Riesen at:
> http://marc.info/?l=linux-kernel&m=126364040821071&w=2
> 

Please don't make this change, it's the user's responsibility
to make sure @len won't exceed @s1's length.

All the string functions of "n" version should work when
@s1 is not null-terminated, so don't call strlen() on @s1.

> Signed-off-by: André Goddard Rosa <andre.goddard@...il.com>
> cc: Li Zefan <lizf@...fujitsu.com>
> cc: Alex Riesen <raa.lkml@...il.com>
> cc: Andrew Morton <akpm@...ux-foundation.org>
> ---
>  lib/string.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/lib/string.c b/lib/string.c
> index 0f86245..94bad34 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -689,11 +689,13 @@ EXPORT_SYMBOL(strstr);
>   */
>  char *strnstr(const char *s1, const char *s2, size_t len)
>  {
> -	size_t l1 = len, l2;
> +	size_t l1, l2;
>  
>  	l2 = strlen(s2);
>  	if (!l2)
>  		return (char *)s1;
> +	l1 = strlen(s1);
> +	l1 = (l1 <= len) ? l1 : len;
>  	while (l1 >= l2) {
>  		l1--;
>  		if (!memcmp(s1, s2, l2))
--
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