linux-kernel - Re: [PATCH 3/4] security/selinux: decrement sizeof size in strncmp

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Date:	Thu, 12 Nov 2009 19:16:14 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Julia Lawall <julia@...u.dk>
cc:	Stephen Smalley <sds@...ho.nsa.gov>,
	Eric Paris <eparis@...isplace.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 3/4] security/selinux: decrement sizeof size in strncmp

On Thu, 12 Nov 2009, Julia Lawall wrote:

> From: Julia Lawall <julia@...u.dk>
> 
> As observed by Joe Perches, sizeof of a constant string includes the
> trailing 0.  If what is wanted is to check the initial characters of
> another string, this trailing 0 should not be taken into account.  If an
> exact match is wanted, strcmp should be used instead.

> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -448,7 +448,7 @@ static int sb_finish_set_opts(struct sup
>  		sbsec->flags &= ~SE_SBLABELSUPP;
>  
>  	/* Special handling for sysfs. Is genfs but also has setxattr handler*/
> -	if (strncmp(sb->s_type->name, "sysfs", sizeof("sysfs")) == 0)
> +	if (strncmp(sb->s_type->name, "sysfs", sizeof("sysfs") - 1) == 0)
>  		sbsec->flags |= SE_SBLABELSUPP;

Shouldn't this be a simple strcmp() ?


-- 
James Morris
<jmorris@...ei.org>
--
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