linux-kernel - Re: [PATCH] apparmor: fix SECURITY_APPARMOR_HASH

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Date:	Wed, 13 Jul 2016 14:14:35 -0700
From:	John Johansen <john.johansen@...onical.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] apparmor: fix SECURITY_APPARMOR_HASH_DEFAULT parameter
 handling

On 07/13/2016 01:50 PM, Arnd Bergmann wrote:
> The newly added Kconfig option could never work and just causes a build error
> when disabled:
> 
> security/apparmor/lsm.c:675:25: error: 'CONFIG_SECURITY_APPARMOR_HASH_DEFAULT' undeclared here (not in a function)
>  bool aa_g_hash_policy = CONFIG_SECURITY_APPARMOR_HASH_DEFAULT;
> 
> The problem is that the macro undefined in this case, and we need to use the IS_ENABLED()
> helper to turn it into a boolean constant.
> 
oops yep, looks like I've built with Y and N but not left undefined

> Another minor problem with the original patch is that the option is even offered
> in sysfs when SECURITY_APPARMOR_HASH is not enabled, so this also hides the option
> in that case.
> 
ah yeah nice

also nice that you pulled the condition check into the calc_profile_hash() fn so the
check won't get accidentally dropped by something else calling it
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
Acked-by: John Johansen <john.johansen@...onical.com>

> Fixes: 6059f71f1e94 ("apparmor: add parameter to control whether policy hashing is used")
> ---
>  security/apparmor/crypto.c        | 3 +++
>  security/apparmor/lsm.c           | 4 +++-
>  security/apparmor/policy_unpack.c | 3 +--
>  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/security/apparmor/crypto.c b/security/apparmor/crypto.c
> index 532471d0b3a0..b75dab0df1cb 100644
> --- a/security/apparmor/crypto.c
> +++ b/security/apparmor/crypto.c
> @@ -39,6 +39,9 @@ int aa_calc_profile_hash(struct aa_profile *profile, u32 version, void *start,
>  	int error = -ENOMEM;
>  	u32 le32_version = cpu_to_le32(version);
>  
> +	if (!aa_g_hash_policy)
> +		return 0;
> +
>  	if (!apparmor_tfm)
>  		return 0;
>  
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 3be30c701bfa..41b8cb115801 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -671,9 +671,11 @@ enum profile_mode aa_g_profile_mode = APPARMOR_ENFORCE;
>  module_param_call(mode, param_set_mode, param_get_mode,
>  		  &aa_g_profile_mode, S_IRUSR | S_IWUSR);
>  
> +#ifdef CONFIG_SECURITY_APPARMOR_HASH
>  /* whether policy verification hashing is enabled */
> -bool aa_g_hash_policy = CONFIG_SECURITY_APPARMOR_HASH_DEFAULT;
> +bool aa_g_hash_policy = IS_ENABLED(CONFIG_SECURITY_APPARMOR_HASH_DEFAULT);
>  module_param_named(hash_policy, aa_g_hash_policy, aabool, S_IRUSR | S_IWUSR);
> +#endif
>  
>  /* Debug mode */
>  bool aa_g_debug;
> diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
> index b9b1c66a32a5..138120698f83 100644
> --- a/security/apparmor/policy_unpack.c
> +++ b/security/apparmor/policy_unpack.c
> @@ -778,8 +778,7 @@ int aa_unpack(void *udata, size_t size, struct list_head *lh, const char **ns)
>  		if (error)
>  			goto fail_profile;
>  
> -		if (aa_g_hash_policy)
> -			error = aa_calc_profile_hash(profile, e.version, start,
> +		error = aa_calc_profile_hash(profile, e.version, start,
>  						     e.pos - start);
>  		if (error)
>  			goto fail_profile;
>