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

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Date:	Thu, 12 Nov 2009 18:11:55 -0800
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	James Morris <jmorris@...ei.org>
CC:	Julia Lawall <julia@...u.dk>, "Serge E. Hallyn" <serue@...ibm.com>,
	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

James Morris wrote:
> On Thu, 12 Nov 2009, Casey Schaufler wrote:
>
>   
>> I strongly suggest that this is not what is wanted.
>>     strcmp(x,y)
>> and
>>     strncmp(x,y,sizeof(y))
>>
>> are functionally equivalent and strcmp has a bad reputation in
>> the security community because it is associated with potential
>> buffer overrun issues.
>>     
>
> Do you see potential for a buffer overrun in this case?
>   

No, but I hate arguing with people who think that every time
they see strcmp that they have found a security flaw. The
existing code does exactly what it is intended to. Why make
a change that just clutters things up?

> The strings being compared are "sysfs" and the name field of 'struct 
> file_system_type'.  The kernel code elsewhere assumes the latter string to 
> be a valid zero-terminated string, and we should, too.
>
>
> - James
>   

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