linux-kernel - Re: [PATCH 2/2] smack: fix logic in smack_inode_init

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Date:	Mon, 01 Dec 2014 13:34:01 -0800
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Lukasz Pawelczyk <l.pawelczyk@...sung.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
CC:	Lukasz Pawelczyk <havner@...il.com>
Subject: Re: [PATCH 2/2] smack: fix logic in smack_inode_init_security function

On 11/26/2014 6:31 AM, Lukasz Pawelczyk wrote:
> In principle if this function was called with "value" == NULL and "len"
> not NULL it could return different results for the "len" compared to a
> case where "name" was not NULL. This is a hypothetical case that does
> not exist in the kernel, but it's a logic bug nonetheless.
>
> Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@...sung.com>

Applied to git://git.gitorious.org/smack-next/kernel.git#smack-for-3.20

> ---
>  security/smack/smack_lsm.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index d1b14d5..e8bed86 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -800,7 +800,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  	if (name)
>  		*name = XATTR_SMACK_SUFFIX;
>  
> -	if (value) {
> +	if (value && len) {
>  		rcu_read_lock();
>  		may = smk_access_entry(skp->smk_known, dsp->smk_known,
>  				       &skp->smk_rules);
> @@ -821,10 +821,9 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  		*value = kstrdup(isp->smk_known, GFP_NOFS);
>  		if (*value == NULL)
>  			return -ENOMEM;
> -	}
>  
> -	if (len)
>  		*len = strlen(isp->smk_known);
> +	}
>  
>  	return 0;
>  }

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