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Date:	Fri, 8 Aug 2014 22:51:37 +0200
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Konstantin Khlebnikov <k.khlebnikov@...sung.com>
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>
Subject: Re: [PATCH 3/3] Smack: remove unneeded NULL-termination from
 securtity label

Quoting Konstantin Khlebnikov (k.khlebnikov@...sung.com):
> Values of extended attributes are stored as binary blobs. NULL-termination
> of them isn't required. It just wastes disk space and confuses command-line
> tools like getfattr because they have to print that zero byte at the end.
> 
> This patch removes terminating zero byte from initial security label in
> smack_inode_init_security and cuts it out in function smack_inode_getsecurity
> which is used by syscall getxattr. This change seems completely safe, because
> function smk_parse_smack ignores everything after first zero byte.
> 
> Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@...sung.com>

selinux doesn't seem to do it this way, and apparmor doesn't use these
at all, but your reasoning does seem correct.

Acked-by: Serge Hallyn <serge.hallyn@...onical.com>

> ---
>  security/smack/smack_lsm.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index afa5ad0..16ae853 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -672,7 +672,7 @@ static int smack_inode_init_security(struct inode *inode, struct inode *dir,
>  	}
>  
>  	if (len)
> -		*len = strlen(isp) + 1;
> +		*len = strlen(isp);
>  
>  	return 0;
>  }
> @@ -1076,7 +1076,7 @@ static int smack_inode_getsecurity(const struct inode *inode,
>  
>  	if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
>  		isp = smk_of_inode(inode);
> -		ilen = strlen(isp) + 1;
> +		ilen = strlen(isp);
>  		*buffer = isp;
>  		return ilen;
>  	}
> @@ -1101,7 +1101,7 @@ static int smack_inode_getsecurity(const struct inode *inode,
>  	else
>  		return -EOPNOTSUPP;
>  
> -	ilen = strlen(isp) + 1;
> +	ilen = strlen(isp);
>  	if (rc == 0) {
>  		*buffer = isp;
>  		rc = ilen;
--
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