linux-kernel - Re: [PATCH] (2.6.24-rc3-mm2) -mm Smack mutex cleanup

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Date:	Tue, 04 Dec 2007 00:20:32 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	casey@...aufler-ca.com
CC:	akpm@...l.org, torvalds@...l.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] (2.6.24-rc3-mm2) -mm Smack mutex cleanup

On 12/03/2007 07:39 PM, Casey Schaufler wrote:
> From: Casey Schaufler <casey@...aufler-ca.com>
> 
> Clean out unnecessary mutex initializations for Smack list locks.
> Once this is done, there is no need for them to be shared among
> multiple files, so pull them out of the header file and put them
> in the files where they belong.

Then it might be static.

> Pull unnecessary locking from smack_inode_setsecurity, it used
> to be required when the assignment was not guaranteed to be a
> scalar value but isn't now.
> 
> Change uses of __capable(current,...) to capable(...).
> Take out an inappropriate cast. Use container_of() instead
> of doing the same calculation by hand.
> Fix comment spelling errors.

Too many different changes according to the name of the patch.

> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> 
> ---
> 
> Tested with stamp-2007-11-30-16-39
> 
>  security/smack/smack.h        |    3 --
>  security/smack/smack_access.c |    3 ++
>  security/smack/smack_lsm.c    |   34 +++++++++-----------------------
>  security/smack/smackfs.c      |    6 +++++
>  4 files changed, 19 insertions(+), 27 deletions(-)
> 
> diff -uprN -X linux-2.6.24-rc3-mm2-base/Documentation/dontdiff linux-2.6.24-rc3-mm2-base/security/smack/smack_lsm.c linux-2.6.24-rc3-mm2-smack/security/smack/smack_lsm.c
> --- linux-2.6.24-rc3-mm2-base/security/smack/smack_lsm.c	2007-11-27 16:47:05.000000000 -0800
> +++ linux-2.6.24-rc3-mm2-smack/security/smack/smack_lsm.c	2007-11-28 11:46:13.000000000 -0800
[...]
> @@ -748,9 +746,7 @@ static int smack_inode_setsecurity(struc
>  		return -EINVAL;
>  
>  	if (strcmp(name, XATTR_SMACK_SUFFIX) == 0) {
> -		mutex_lock(&nsp->smk_lock);
>  		nsp->smk_inode = sp;
> -		mutex_unlock(&nsp->smk_lock);
>  		return 0;
>  	}
>  	/*

Ok, it still might be atomic as a variable change, but it will break scenarios
such as

mutex_lock(&nsp->smk_lock);
create(nsp->smk_inode);
cook_a_dinner();
get_info(nsp->smk_inode);
mutex_unlock(&nsp->smk_lock);

While cook_a_dinner(), smack_inode_setsecurity() is called and the attribute
changed...

Doesn't this matter?
--
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