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

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Message-ID: <4AFE1EA9.60102@schaufler-ca.com>
Date:	Fri, 13 Nov 2009 19:06:17 -0800
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Valdis.Kletnieks@...edu
CC:	James Morris <jmorris@...ei.org>, 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

Valdis.Kletnieks@...edu wrote:
> On Thu, 12 Nov 2009 18:11:55 PST, Casey Schaufler said:
>   
>> James Morris wrote:
>>     
>>> 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.
>>     
>
> How do you feel about people who think every time they see strcmp()
> "Oh crap, something that needs auditing"? ;)
>   

They have my deep sympathy. Which is why I'm advocating leaving
the perfectly functional and correct use of strncmp() as it is.

> The biggest problem with strcmp() is that even if it got audited when that code
> went in, it's prone to unaudited breakage when somebody changes something in
> some other piece of code, quite often in some other .c file in some other
> directory.
>
> Julia, is there a way to use coccinelle to detect unsafe changes like that?  Or
> is expressing those semantics too difficult?
>
>
>   

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