linux-kernel - Re: [ 010/122] smack: off by one error

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Date:	Tue, 07 Aug 2012 17:11:22 -0700
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Alan Cox <alan@...ux.intel.com>,
	James Morris <james.l.morris@...cle.com>,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [ 010/122] smack: off by one error

On 8/7/2012 3:24 PM, Greg Kroah-Hartman wrote:
> From: Greg KH <gregkh@...uxfoundation.org>
>
> 3.5-stable review patch.  If anyone has any objections, please let me know.

No objection here.

>
> ------------------
>
> From: Alan Cox <alan@...ux.intel.com>
>
> commit 3b9fc37280c521b086943f9aedda767f5bf3b2d3 upstream.
>
> Consider the input case of a rule that consists entirely of non space
> symbols followed by a \0. Say 64 + \0
>
> In this case strlen(data) = 64
> kzalloc of subject and object are 64 byte objects
> sscanfdata, "%s %s %s", subject, ...)
>
> will put 65 bytes into subject.
>
> Signed-off-by: Alan Cox <alan@...ux.intel.com>
> Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> Signed-off-by: James Morris <james.l.morris@...cle.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> ---
>  security/smack/smackfs.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -325,11 +325,11 @@ static int smk_parse_long_rule(const cha
>  	int datalen;
>  	int rc = -1;
>  
> -	/*
> -	 * This is probably inefficient, but safe.
> -	 */
> +	/* This is inefficient */
>  	datalen = strlen(data);
> -	subject = kzalloc(datalen, GFP_KERNEL);
> +
> +	/* Our first element can be 64 + \0 with no spaces */
> +	subject = kzalloc(datalen + 1, GFP_KERNEL);
>  	if (subject == NULL)
>  		return -1;
>  	object = kzalloc(datalen, GFP_KERNEL);
>
>
> --
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