linux-kernel - Re: [RFC][PATCH v2 2/7] implement memmem()

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Date:	Fri, 06 Feb 2015 23:30:19 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH v2 2/7] implement memmem()

On Fri, Feb 06 2015, Al Viro <viro@...IV.linux.org.uk> wrote:

> +/**
> + * strnstr - Find the first substring in a length-limited string
> + * @s1: The string to be searched
> + * @s2: The string to search for
> + * @len: the maximum number of characters to search
> + */
> +char *strnstr(const char *s1, const char *s2, size_t len)
> +{
> +	return memmem(s1, len, s2, strlen(s2));
> +}

Most strn* interfaces don't require the n to be at most the actual
string length, but it seems that this would happily search past the '\0'
of s1 if len is large enough, e.g.

strnstr("abc\0def", "def", 1000)

will not return NULL (unlike what the libbsd version does). So either
that restriction should be documented or len should be replaced by
min(len, strlen(s1)).

Rasmus

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