[PATCH BUGFIX -rc3] Smack: Don't register smackfs if we're not loaded

[PATCH BUGFIX -rc3] Smack: Don't register smackfs if we're not loaded

[Ahmed S. Darwish]

Hi all,

Smackfs initialization without an enabled Smack leads to
an early Oops that renders the system unusable.

Introduce a global smack_enabled variable that will be used
to make sure that no smack components will be registered 
(ala smackfs) if we are not already enabled.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
---

The Oops is triggered by the security= patch that will be sent
soon.

I can't imagine an SELinux guru finding /smackfs instead of 
his usual /selinuxfs when he hits a tab completion after 's' ;).
As a bonus, this patch will handle that case too.

 smack.h     |    9 +++++++++
 smack_lsm.c |    8 ++++++++
 smackfs.c   |    3 +++

 3 files changed, 20 insertions(+)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index a21a0e9..17c55ad 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -18,6 +18,15 @@
 #include <net/netlabel.h>
 
 /*
+ * We must not bother the rest of the kernel by exporting our
+ * own stuff if we are not already enabled. We may not be loaded
+ * if another or no LSM was chosen on boot.
+ * Smackfs is currently the only exported component, but this
+ * may change in the future.
+ */
+extern int smack_enabled;
+
+/*
  * Why 23? CIPSO is constrained to 30, so a 32 byte buffer is
  * bigger than can be used, and 24 is the next lower multiple
  * of 8, and there are too many issues if there isn't space set
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 770eb06..6fe7869 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -36,6 +36,8 @@
 #define SOCKFS_MAGIC		0x534F434B
 #define TMPFS_MAGIC		0x01021994
 
+int smack_enabled;
+
 /**
  * smk_fetch - Fetch the smack label from a file.
  * @ip: a pointer to the inode
@@ -2589,6 +2591,12 @@ static __init int smack_init(void)
 	if (register_security(&smack_ops))
 		panic("smack: Unable to register with kernel.\n");
 
+	/*
+	 * Notify other Smack components that it's now safe to
+	 * to register themselves.
+	 */
+	smack_enabled = 1;
+
 	return 0;
 }
 
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 358c92c..e1687c0 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -992,6 +992,9 @@ static int __init init_smk_fs(void)
 {
 	int err;
 
+	if (!smack_enabled)
+		return 0;
+
 	err = register_filesystem(&smk_fs_type);
 	if (!err) {
 		smackfs_mount = kern_mount(&smk_fs_type);

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

[PATCH -rc3] Security: Introduce security= boot parameter

[Ahmed S. Darwish]

Hi all,

[
    Sending as a reply to the above Smack bugfix cause the bug 
    is triggered by this patch.

    Please merge the bugfix before this.

    IMHO this patch (or similar) is needed before the release
    to avoid useless panics. Also as noted by Alexey, current
    allyesconfig kernels panics cause of the same problem which
    means less testing before hitting 2.6.25 .

    Thanks!
]

-->

Add the security= boot parameter. This is done to avoid LSM 
registration clashes in case of more than one bult-in module.

User can choose a security module to enable at boot. If no 
security= boot parameter is specified, only the first LSM 
asking for registration will be loaded. An invalid security 
module name will be treated as if no module has been chosen.

LSM modules must check now if they are allowed to register
by calling security_module_enable(ops) first. Modify SELinux 
and SMACK to do so.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
Acked-by: James Morris <jmorris@namei.org>
Reported-by: Alexey Dobriyan <adobriyan@sw.ru>
---

[James ACKed the -mm version, but this patch is exactly the same]

 Documentation/kernel-parameters.txt |    6 ++++
 include/linux/security.h            |   12 +++++++++
 security/dummy.c                    |    2 -
 security/security.c                 |   46 +++++++++++++++++++++++++++++++++++-
 security/selinux/hooks.c            |    7 +++++
 security/smack/smack_lsm.c          |    5 +++
 6 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9a5b665..64efbdc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -374,6 +374,12 @@ and is between 256 and 4096 characters. It is defined in the file
 			possible to determine what the correct size should be.
 			This option provides an override for these situations.
 
+	security=	[SECURITY] Choose a security module to enable at boot. 
+			If this boot parameter is not specified, only the first 
+			security module asking for security registration will be
+			loaded. An invalid security module name will be treated
+			as if no module has been chosen.
+
 	capability.disable=
 			[SECURITY] Disable capabilities.  This would normally
 			be used only if an alternative security model is to be
diff --git a/include/linux/security.h b/include/linux/security.h
index fe52cde..801c9ad 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -42,6 +42,9 @@
 
 extern unsigned securebits;
 
+/* Maximum number of letters for an LSM name string */
+#define SECURITY_NAME_MAX	10
+
 struct ctl_table;
 
 /*
@@ -117,6 +120,12 @@ struct request_sock;
 /**
  * struct security_operations - main security structure
  *
+ * Security module identifier.
+ *
+ * @name:
+ *	A string that acts as a unique identifeir for the LSM with max number
+ *	of characters = SECURITY_NAME_MAX.
+ *
  * Security hooks for program execution operations.
  *
  * @bprm_alloc_security:
@@ -1207,6 +1216,8 @@ struct request_sock;
  * This is the main security structure.
  */
 struct security_operations {
+	char name[SECURITY_NAME_MAX + 1];
+
 	int (*ptrace) (struct task_struct * parent, struct task_struct * child);
 	int (*capget) (struct task_struct * target,
 		       kernel_cap_t * effective,
@@ -1466,6 +1477,7 @@ struct security_operations {
 
 /* prototypes */
 extern int security_init	(void);
+extern int security_module_enable(struct security_operations *ops);
 extern int register_security	(struct security_operations *ops);
 extern int mod_reg_security	(const char *name, struct security_operations *ops);
 extern struct dentry *securityfs_create_file(const char *name, mode_t mode,
diff --git a/security/dummy.c b/security/dummy.c
index 649326b..96d196f 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -979,7 +979,7 @@ static inline int dummy_key_permission(key_ref_t key_ref,
 }
 #endif /* CONFIG_KEYS */
 
-struct security_operations dummy_security_ops;
+struct security_operations dummy_security_ops = { "dummy" };
 
 #define set_to_dummy_if_null(ops, function)				\
 	do {								\
diff --git a/security/security.c b/security/security.c
index d15e56c..f188672 100644
--- a/security/security.c
+++ b/security/security.c
@@ -17,6 +17,9 @@
 #include <linux/kernel.h>
 #include <linux/security.h>
 
+/* Boot-time LSM user choice */
+static spinlock_t chosen_lsm_lock;
+static char chosen_lsm[SECURITY_NAME_MAX + 1];
 
 /* things that live in dummy.c */
 extern struct security_operations dummy_security_ops;
@@ -62,18 +65,59 @@ int __init security_init(void)
 	}
 
 	security_ops = &dummy_security_ops;
+	spin_lock_init(&chosen_lsm_lock);
 	do_security_initcalls();
 
 	return 0;
 }
 
+/* Save user chosen LSM */
+static int __init choose_lsm(char *str)
+{
+	strncpy(chosen_lsm, str, SECURITY_NAME_MAX);
+	return 1;
+}
+__setup("security=", choose_lsm);
+
+/**
+ * security_module_enable - Load given security module on boot ?
+ * @ops: a pointer to the struct security_operations that is to be checked.
+ *
+ * Each LSM must pass this method before registering its own operations
+ * to avoid security registration races.
+ *
+ * Return true if:
+ *	-The passed LSM is the one chosen by user at boot time,
+ *	-or user didsn't specify a specific LSM and we're the first to ask
+ *	 for registeration permissoin.
+ * Otherwise, return false.
+ */
+int security_module_enable(struct security_operations *ops)
+{
+	int rc = 1;
+
+	spin_lock(&chosen_lsm_lock);
+	if (!*chosen_lsm)
+		strncpy(chosen_lsm, ops->name, SECURITY_NAME_MAX);
+	else if (strncmp(ops->name, chosen_lsm, SECURITY_NAME_MAX))
+		rc = 0;
+	spin_unlock(&chosen_lsm_lock);
+
+	if (rc)
+		printk(KERN_INFO "Security: Loading '%s' security module.\n",
+		       ops->name);
+
+	return rc;
+}
+
 /**
  * register_security - registers a security framework with the kernel
  * @ops: a pointer to the struct security_options that is to be registered
  *
  * This function is to allow a security module to register itself with the
  * kernel security subsystem.  Some rudimentary checking is done on the @ops
- * value passed to this function.
+ * value passed to this function. You'll need to check first if your LSM
+ * is allowed to register its @ops by calling security_module_enable(@ops).
  *
  * If there is already a security module registered with the kernel,
  * an error will be returned.  Otherwise 0 is returned on success.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 75c2e99..49709a4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5219,6 +5219,8 @@ static int selinux_key_permission(key_ref_t key_ref,
 #endif
 
 static struct security_operations selinux_ops = {
+	.name =				"selinux",
+
 	.ptrace =			selinux_ptrace,
 	.capget =			selinux_capget,
 	.capset_check =			selinux_capset_check,
@@ -5405,6 +5407,11 @@ static __init int selinux_init(void)
 {
 	struct task_security_struct *tsec;
 
+	if (!security_module_enable(&selinux_ops)) {
+		selinux_enabled = 0;
+		return 0;
+	}
+
 	if (!selinux_enabled) {
 		printk(KERN_INFO "SELinux:  Disabled at boot.\n");
 		return 0;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6fe7869..ecf1d16 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2436,6 +2436,8 @@ static void smack_release_secctx(char *secdata, u32 seclen)
 }
 
 static struct security_operations smack_ops = {
+	.name =				"smack",
+
 	.ptrace = 			smack_ptrace,
 	.capget = 			cap_capget,
 	.capset_check = 		cap_capset_check,
@@ -2568,6 +2570,9 @@ static struct security_operations smack_ops = {
  */
 static __init int smack_init(void)
 {
+	if (!security_module_enable(&smack_ops))
+		return 0;
+
 	printk(KERN_INFO "Smack:  Initializing.\n");
 
 	/*


If you read till here, Thank you for the review ;)
Regards,

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

[PATCH -v7 -rc3] Security: Introduce security= boot parameter

[Ahmed S. Darwish]

Hi!,

[
    Our usual changelog:

    - Fold the SMACK bugfix here cause now it depends on the
      new introduced security_ symbol.
    - Do not register smackfs if Smack was not loaded
    - Do not use a global to check if Smack was enabled, use 
      security_module_enable(ops) instead.
    - Export smack_ops security operations to the rest of
      SMACK code to satisfy above point.
    - Remove James ACK cause patch semantics changed (could you
      please reACK ?).
]

-->

Add the security= boot parameter. This is done to avoid LSM 
registration clashes in case of more than one bult-in module.

User can choose a security module to enable at boot. If no 
security= boot parameter is specified, only the first LSM 
asking for registration will be loaded. An invalid security 
module name will be treated as if no module has been chosen.

LSM modules must check now if they are allowed to register
by calling security_module_enable(ops) first. Modify SELinux 
and SMACK to do so.

Do not let SMACK register smackfs if it was not chosen on
boot. Smackfs assumes that smack hooks are registered and
the initial task security setup (swapper->security) is done.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
Reported-by: Alexey Dobriyan <adobriyan@sw.ru>
---

 Documentation/kernel-parameters.txt |    6 ++++
 include/linux/security.h            |   12 +++++++++
 security/dummy.c                    |    2 -
 security/security.c                 |   46 +++++++++++++++++++++++++++++++++++-
 security/selinux/hooks.c            |    7 +++++
 security/smack/smack.h              |    2 +
 security/smack/smack_lsm.c          |    7 ++++-
 security/smack/smackfs.c            |    9 ++++++-

 8 files changed, 87 insertions(+), 4 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9a5b665..64efbdc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -374,6 +374,12 @@ and is between 256 and 4096 characters. It is defined in the file
 			possible to determine what the correct size should be.
 			This option provides an override for these situations.
 
+	security=	[SECURITY] Choose a security module to enable at boot. 
+			If this boot parameter is not specified, only the first 
+			security module asking for security registration will be
+			loaded. An invalid security module name will be treated
+			as if no module has been chosen.
+
 	capability.disable=
 			[SECURITY] Disable capabilities.  This would normally
 			be used only if an alternative security model is to be
diff --git a/include/linux/security.h b/include/linux/security.h
index fe52cde..801c9ad 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -42,6 +42,9 @@
 
 extern unsigned securebits;
 
+/* Maximum number of letters for an LSM name string */
+#define SECURITY_NAME_MAX	10
+
 struct ctl_table;
 
 /*
@@ -117,6 +120,12 @@ struct request_sock;
 /**
  * struct security_operations - main security structure
  *
+ * Security module identifier.
+ *
+ * @name:
+ *	A string that acts as a unique identifeir for the LSM with max number
+ *	of characters = SECURITY_NAME_MAX.
+ *
  * Security hooks for program execution operations.
  *
  * @bprm_alloc_security:
@@ -1207,6 +1216,8 @@ struct request_sock;
  * This is the main security structure.
  */
 struct security_operations {
+	char name[SECURITY_NAME_MAX + 1];
+
 	int (*ptrace) (struct task_struct * parent, struct task_struct * child);
 	int (*capget) (struct task_struct * target,
 		       kernel_cap_t * effective,
@@ -1466,6 +1477,7 @@ struct security_operations {
 
 /* prototypes */
 extern int security_init	(void);
+extern int security_module_enable(struct security_operations *ops);
 extern int register_security	(struct security_operations *ops);
 extern int mod_reg_security	(const char *name, struct security_operations *ops);
 extern struct dentry *securityfs_create_file(const char *name, mode_t mode,
diff --git a/security/dummy.c b/security/dummy.c
index 649326b..96d196f 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -979,7 +979,7 @@ static inline int dummy_key_permission(key_ref_t key_ref,
 }
 #endif /* CONFIG_KEYS */
 
-struct security_operations dummy_security_ops;
+struct security_operations dummy_security_ops = { "dummy" };
 
 #define set_to_dummy_if_null(ops, function)				\
 	do {								\
diff --git a/security/security.c b/security/security.c
index d15e56c..f188672 100644
--- a/security/security.c
+++ b/security/security.c
@@ -17,6 +17,9 @@
 #include <linux/kernel.h>
 #include <linux/security.h>
 
+/* Boot-time LSM user choice */
+static spinlock_t chosen_lsm_lock;
+static char chosen_lsm[SECURITY_NAME_MAX + 1];
 
 /* things that live in dummy.c */
 extern struct security_operations dummy_security_ops;
@@ -62,18 +65,59 @@ int __init security_init(void)
 	}
 
 	security_ops = &dummy_security_ops;
+	spin_lock_init(&chosen_lsm_lock);
 	do_security_initcalls();
 
 	return 0;
 }
 
+/* Save user chosen LSM */
+static int __init choose_lsm(char *str)
+{
+	strncpy(chosen_lsm, str, SECURITY_NAME_MAX);
+	return 1;
+}
+__setup("security=", choose_lsm);
+
+/**
+ * security_module_enable - Load given security module on boot ?
+ * @ops: a pointer to the struct security_operations that is to be checked.
+ *
+ * Each LSM must pass this method before registering its own operations
+ * to avoid security registration races.
+ *
+ * Return true if:
+ *	-The passed LSM is the one chosen by user at boot time,
+ *	-or user didsn't specify a specific LSM and we're the first to ask
+ *	 for registeration permissoin.
+ * Otherwise, return false.
+ */
+int security_module_enable(struct security_operations *ops)
+{
+	int rc = 1;
+
+	spin_lock(&chosen_lsm_lock);
+	if (!*chosen_lsm)
+		strncpy(chosen_lsm, ops->name, SECURITY_NAME_MAX);
+	else if (strncmp(ops->name, chosen_lsm, SECURITY_NAME_MAX))
+		rc = 0;
+	spin_unlock(&chosen_lsm_lock);
+
+	if (rc)
+		printk(KERN_INFO "Security: Loading '%s' security module.\n",
+		       ops->name);
+
+	return rc;
+}
+
 /**
  * register_security - registers a security framework with the kernel
  * @ops: a pointer to the struct security_options that is to be registered
  *
  * This function is to allow a security module to register itself with the
  * kernel security subsystem.  Some rudimentary checking is done on the @ops
- * value passed to this function.
+ * value passed to this function. You'll need to check first if your LSM
+ * is allowed to register its @ops by calling security_module_enable(@ops).
  *
  * If there is already a security module registered with the kernel,
  * an error will be returned.  Otherwise 0 is returned on success.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 75c2e99..49709a4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5219,6 +5219,8 @@ static int selinux_key_permission(key_ref_t key_ref,
 #endif
 
 static struct security_operations selinux_ops = {
+	.name =				"selinux",
+
 	.ptrace =			selinux_ptrace,
 	.capget =			selinux_capget,
 	.capset_check =			selinux_capset_check,
@@ -5405,6 +5407,11 @@ static __init int selinux_init(void)
 {
 	struct task_security_struct *tsec;
 
+	if (!security_module_enable(&selinux_ops)) {
+		selinux_enabled = 0;
+		return 0;
+	}
+
 	if (!selinux_enabled) {
 		printk(KERN_INFO "SELinux:  Disabled at boot.\n");
 		return 0;
diff --git a/security/smack/smack.h b/security/smack/smack.h
index a21a0e9..c444f48 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -15,6 +15,7 @@
 
 #include <linux/capability.h>
 #include <linux/spinlock.h>
+#include <linux/security.h>
 #include <net/netlabel.h>
 
 /*
@@ -195,6 +196,7 @@ extern struct smack_known smack_known_star;
 extern struct smack_known smack_known_unset;
 
 extern struct smk_list_entry *smack_list;
+extern struct security_operations smack_ops;
 
 /*
  * Stricly for CIPSO level manipulation.
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 770eb06..afa7967 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2433,7 +2433,9 @@ static void smack_release_secctx(char *secdata, u32 seclen)
 {
 }
 
-static struct security_operations smack_ops = {
+struct security_operations smack_ops = {
+	.name =				"smack",
+
 	.ptrace = 			smack_ptrace,
 	.capget = 			cap_capget,
 	.capset_check = 		cap_capset_check,
@@ -2566,6 +2568,9 @@ static struct security_operations smack_ops = {
  */
 static __init int smack_init(void)
 {
+	if (!security_module_enable(&smack_ops))
+		return 0;
+
 	printk(KERN_INFO "Smack:  Initializing.\n");
 
 	/*
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 358c92c..769da9a 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -986,12 +986,19 @@ static struct vfsmount *smackfs_mount;
  *
  * register the smackfs
  *
- * Returns 0 unless the registration fails.
+ * Do not register smackfs if Smack wasn't enabled
+ * on boot.
+ *
+ * Returns true if we were not chosen on boot or if
+ * we were chosen and filesystem registration succeeded.
  */
 static int __init init_smk_fs(void)
 {
 	int err;
 
+	if (!security_module_enable(&smack_ops))
+		return 0;
+
 	err = register_filesystem(&smk_fs_type);
 	if (!err) {
 		smackfs_mount = kern_mount(&smk_fs_type);

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

Re: [PATCH -v7 -rc3] Security: Introduce security= boot parameter

[Casey Schaufler]

--- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:

> Hi!,
> 
> [
>     Our usual changelog:
> 
>     - Fold the SMACK bugfix here cause now it depends on the
>       new introduced security_ symbol.
>     - Do not register smackfs if Smack was not loaded
>     - Do not use a global to check if Smack was enabled, use 
>       security_module_enable(ops) instead.
>     - Export smack_ops security operations to the rest of
>       SMACK code to satisfy above point.
>     - Remove James ACK cause patch semantics changed (could you
>       please reACK ?).
> ]
> 
> -->
> 
> Add the security= boot parameter. This is done to avoid LSM 
> registration clashes in case of more than one bult-in module.
> 
> User can choose a security module to enable at boot. If no 
> security= boot parameter is specified, only the first LSM 
> asking for registration will be loaded. An invalid security 
> module name will be treated as if no module has been chosen.
> 
> LSM modules must check now if they are allowed to register
> by calling security_module_enable(ops) first. Modify SELinux 
> and SMACK to do so.
> 
> Do not let SMACK register smackfs if it was not chosen on
> boot. Smackfs assumes that smack hooks are registered and
> the initial task security setup (swapper->security) is done.

If the problem with initializing smackfs is because the
locks aren't initialized why not leave the lock initializations
in smack_init, and have them done before the check to see if the
smack LSM is going to get used? Really, we're only talking
about the case where a kernel is configured for testing or
development purposes, and the lock initialization can't
be considered a major impact in any case.

> Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
> Reported-by: Alexey Dobriyan <adobriyan@sw.ru>
> ---
> 
>  Documentation/kernel-parameters.txt |    6 ++++
>  include/linux/security.h            |   12 +++++++++
>  security/dummy.c                    |    2 -
>  security/security.c                 |   46
> +++++++++++++++++++++++++++++++++++-
>  security/selinux/hooks.c            |    7 +++++
>  security/smack/smack.h              |    2 +
>  security/smack/smack_lsm.c          |    7 ++++-
>  security/smack/smackfs.c            |    9 ++++++-
> 
>  8 files changed, 87 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt
> index 9a5b665..64efbdc 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -374,6 +374,12 @@ and is between 256 and 4096 characters. It is defined in
> the file
>  			possible to determine what the correct size should be.
>  			This option provides an override for these situations.
>  
> +	security=	[SECURITY] Choose a security module to enable at boot. 
> +			If this boot parameter is not specified, only the first 
> +			security module asking for security registration will be
> +			loaded. An invalid security module name will be treated
> +			as if no module has been chosen.
> +
>  	capability.disable=
>  			[SECURITY] Disable capabilities.  This would normally
>  			be used only if an alternative security model is to be
> diff --git a/include/linux/security.h b/include/linux/security.h
> index fe52cde..801c9ad 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -42,6 +42,9 @@
>  
>  extern unsigned securebits;
>  
> +/* Maximum number of letters for an LSM name string */
> +#define SECURITY_NAME_MAX	10
> +
>  struct ctl_table;
>  
>  /*
> @@ -117,6 +120,12 @@ struct request_sock;
>  /**
>   * struct security_operations - main security structure
>   *
> + * Security module identifier.
> + *
> + * @name:
> + *	A string that acts as a unique identifeir for the LSM with max number
> + *	of characters = SECURITY_NAME_MAX.
> + *
>   * Security hooks for program execution operations.
>   *
>   * @bprm_alloc_security:
> @@ -1207,6 +1216,8 @@ struct request_sock;
>   * This is the main security structure.
>   */
>  struct security_operations {
> +	char name[SECURITY_NAME_MAX + 1];
> +
>  	int (*ptrace) (struct task_struct * parent, struct task_struct * child);
>  	int (*capget) (struct task_struct * target,
>  		       kernel_cap_t * effective,
> @@ -1466,6 +1477,7 @@ struct security_operations {
>  
>  /* prototypes */
>  extern int security_init	(void);
> +extern int security_module_enable(struct security_operations *ops);
>  extern int register_security	(struct security_operations *ops);
>  extern int mod_reg_security	(const char *name, struct security_operations
> *ops);
>  extern struct dentry *securityfs_create_file(const char *name, mode_t mode,
> diff --git a/security/dummy.c b/security/dummy.c
> index 649326b..96d196f 100644
> --- a/security/dummy.c
> +++ b/security/dummy.c
> @@ -979,7 +979,7 @@ static inline int dummy_key_permission(key_ref_t key_ref,
>  }
>  #endif /* CONFIG_KEYS */
>  
> -struct security_operations dummy_security_ops;
> +struct security_operations dummy_security_ops = { "dummy" };
>  
>  #define set_to_dummy_if_null(ops, function)				\
>  	do {								\
> diff --git a/security/security.c b/security/security.c
> index d15e56c..f188672 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -17,6 +17,9 @@
>  #include <linux/kernel.h>
>  #include <linux/security.h>
>  
> +/* Boot-time LSM user choice */
> +static spinlock_t chosen_lsm_lock;
> +static char chosen_lsm[SECURITY_NAME_MAX + 1];
>  
>  /* things that live in dummy.c */
>  extern struct security_operations dummy_security_ops;
> @@ -62,18 +65,59 @@ int __init security_init(void)
>  	}
>  
>  	security_ops = &dummy_security_ops;
> +	spin_lock_init(&chosen_lsm_lock);
>  	do_security_initcalls();
>  
>  	return 0;
>  }
>  
> +/* Save user chosen LSM */
> +static int __init choose_lsm(char *str)
> +{
> +	strncpy(chosen_lsm, str, SECURITY_NAME_MAX);
> +	return 1;
> +}
> +__setup("security=", choose_lsm);
> +
> +/**
> + * security_module_enable - Load given security module on boot ?
> + * @ops: a pointer to the struct security_operations that is to be checked.
> + *
> + * Each LSM must pass this method before registering its own operations
> + * to avoid security registration races.
> + *
> + * Return true if:
> + *	-The passed LSM is the one chosen by user at boot time,
> + *	-or user didsn't specify a specific LSM and we're the first to ask
> + *	 for registeration permissoin.
> + * Otherwise, return false.
> + */
> +int security_module_enable(struct security_operations *ops)
> +{
> +	int rc = 1;
> +
> +	spin_lock(&chosen_lsm_lock);
> +	if (!*chosen_lsm)
> +		strncpy(chosen_lsm, ops->name, SECURITY_NAME_MAX);
> +	else if (strncmp(ops->name, chosen_lsm, SECURITY_NAME_MAX))
> +		rc = 0;
> +	spin_unlock(&chosen_lsm_lock);
> +
> +	if (rc)
> +		printk(KERN_INFO "Security: Loading '%s' security module.\n",
> +		       ops->name);
> +
> +	return rc;
> +}
> +
>  /**
>   * register_security - registers a security framework with the kernel
>   * @ops: a pointer to the struct security_options that is to be registered
>   *
>   * This function is to allow a security module to register itself with the
>   * kernel security subsystem.  Some rudimentary checking is done on the @ops
> - * value passed to this function.
> + * value passed to this function. You'll need to check first if your LSM
> + * is allowed to register its @ops by calling security_module_enable(@ops).
>   *
>   * If there is already a security module registered with the kernel,
>   * an error will be returned.  Otherwise 0 is returned on success.
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 75c2e99..49709a4 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -5219,6 +5219,8 @@ static int selinux_key_permission(key_ref_t key_ref,
>  #endif
>  
>  static struct security_operations selinux_ops = {
> +	.name =				"selinux",
> +
>  	.ptrace =			selinux_ptrace,
>  	.capget =			selinux_capget,
>  	.capset_check =			selinux_capset_check,
> @@ -5405,6 +5407,11 @@ static __init int selinux_init(void)
>  {
>  	struct task_security_struct *tsec;
>  
> +	if (!security_module_enable(&selinux_ops)) {
> +		selinux_enabled = 0;
> +		return 0;
> +	}
> +
>  	if (!selinux_enabled) {
>  		printk(KERN_INFO "SELinux:  Disabled at boot.\n");
>  		return 0;
> diff --git a/security/smack/smack.h b/security/smack/smack.h
> index a21a0e9..c444f48 100644
> --- a/security/smack/smack.h
> +++ b/security/smack/smack.h
> @@ -15,6 +15,7 @@
>  
>  #include <linux/capability.h>
>  #include <linux/spinlock.h>
> +#include <linux/security.h>
>  #include <net/netlabel.h>
>  
>  /*
> @@ -195,6 +196,7 @@ extern struct smack_known smack_known_star;
>  extern struct smack_known smack_known_unset;
>  
>  extern struct smk_list_entry *smack_list;
> +extern struct security_operations smack_ops;
>  
>  /*
>   * Stricly for CIPSO level manipulation.
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 770eb06..afa7967 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -2433,7 +2433,9 @@ static void smack_release_secctx(char *secdata, u32
> seclen)
>  {
>  }
>  
> -static struct security_operations smack_ops = {
> +struct security_operations smack_ops = {
> +	.name =				"smack",
> +
>  	.ptrace = 			smack_ptrace,
>  	.capget = 			cap_capget,
>  	.capset_check = 		cap_capset_check,
> @@ -2566,6 +2568,9 @@ static struct security_operations smack_ops = {
>   */
>  static __init int smack_init(void)
>  {
> +	if (!security_module_enable(&smack_ops))
> +		return 0;
> +
>  	printk(KERN_INFO "Smack:  Initializing.\n");
>  
>  	/*
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index 358c92c..769da9a 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -986,12 +986,19 @@ static struct vfsmount *smackfs_mount;
>   *
>   * register the smackfs
>   *
> - * Returns 0 unless the registration fails.
> + * Do not register smackfs if Smack wasn't enabled
> + * on boot.
> + *
> + * Returns true if we were not chosen on boot or if
> + * we were chosen and filesystem registration succeeded.
>   */
>  static int __init init_smk_fs(void)
>  {
>  	int err;
>  
> +	if (!security_module_enable(&smack_ops))
> +		return 0;
> +
>  	err = register_filesystem(&smk_fs_type);
>  	if (!err) {
>  		smackfs_mount = kern_mount(&smk_fs_type);
> 
> -- 
> 
> "Better to light a candle, than curse the darkness"
> 
> Ahmed S. Darwish
> Homepage: http://darwish.07.googlepages.com
> Blog: http://darwish-07.blogspot.com
> 
> 
> 


Casey Schaufler
casey@schaufler-ca.com

Re: [PATCH -v7 -rc3] Security: Introduce security= boot parameter

[Ahmed S. Darwish]

Hi Casey,

On Wed, Mar 05, 2008 at 08:33:34AM -0800, Casey Schaufler wrote:
> 
> --- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:
> 
...
> > 
> > Do not let SMACK register smackfs if it was not chosen on
> > boot. Smackfs assumes that smack hooks are registered and
> > the initial task security setup (swapper->security) is done.
> 
> If the problem with initializing smackfs is because the
> locks aren't initialized why not leave the lock initializations
> in smack_init, and have them done before the check to see if the
> smack LSM is going to get used? Really, we're only talking
> about the case where a kernel is configured for testing or
> development purposes, and the lock initialization can't
> be considered a major impact in any case.
> 

Beside the locking initialization issue, there's the current->security
issue. smackfs init code code access current->security in 
smk_unlbl_ambient().

As you know current->security may equal Null (Oops), or point to 
another LSM structure that preceeded us in registration. 

The locking argument can't be applied here since we may override
the other LSM tsk->security pointer this time.

Ofcourse all of the above points can be handleded by various
if(current->security) checks + rechecking the read/write methods
of each smackfs inode, but below only two lines will fix the 
problem from its roots ;):

+	if (!security_module_enable(&smack_ops))
+		return 0;

Is there a problem in the current approach that I'm not aware of ?

You have your veto in this issue at the end ;)

Thank you,

-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

Re: [PATCH -v7 -rc3] Security: Introduce security= boot parameter

[Casey Schaufler]

--- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:

> Hi Casey,
> 
> On Wed, Mar 05, 2008 at 08:33:34AM -0800, Casey Schaufler wrote:
> > 
> > --- "Ahmed S. Darwish" <darwish.07@gmail.com> wrote:
> > 
> ...
> > > 
> > > Do not let SMACK register smackfs if it was not chosen on
> > > boot. Smackfs assumes that smack hooks are registered and
> > > the initial task security setup (swapper->security) is done.
> > 
> > If the problem with initializing smackfs is because the
> > locks aren't initialized why not leave the lock initializations
> > in smack_init, and have them done before the check to see if the
> > smack LSM is going to get used? Really, we're only talking
> > about the case where a kernel is configured for testing or
> > development purposes, and the lock initialization can't
> > be considered a major impact in any case.
> > 
> 
> Beside the locking initialization issue, there's the current->security
> issue. smackfs init code code access current->security in 
> smk_unlbl_ambient().
> 
> As you know current->security may equal Null (Oops), or point to 
> another LSM structure that preceeded us in registration. 
> 
> The locking argument can't be applied here since we may override
> the other LSM tsk->security pointer this time.
> 
> Ofcourse all of the above points can be handleded by various
> if(current->security) checks + rechecking the read/write methods
> of each smackfs inode, but below only two lines will fix the 
> problem from its roots ;):
> 
> +	if (!security_module_enable(&smack_ops))
> +		return 0;
> 
> Is there a problem in the current approach that I'm not aware of ?

No, I made the common mistake of replying before I'd read all the
day's threads and didn't have all the information that you did.
Current LSM usage is really unfriendly to multiple "modules". I
don't see any problems with your current approach now that I've
dug into the issues a little further.

> You have your veto in this issue at the end ;)

I suppose, although that would be really stoopid when you're
doing all the hard work. Thank you.


Casey Schaufler
casey@schaufler-ca.com

[PATCH -v7b -rc3] Security: Introduce security= boot parameter

[Ahmed S. Darwish]

Hi!,

[
v7 log:
    - Fold the SMACK bugfix here cause now it depends on the
      new introduced security_ symbol.
    - Do not register smackfs if Smack was not loaded
    - Do not use a global to check if Smack was enabled, use 
      security_module_enable(ops) instead.
    - Export smack_ops security operations to the rest of
      SMACK code to satisfy above point.
    - Remove James ACK cause patch semantics changed (could you
      please reACK ?).      

++:
    - Add in security_module_enable() comments that it may also
      be used to check if our LSM is enabled on boot.
    - Remove the message `Security: %s is loaded, &lsm' from 
      security_module_enable cause of its new usage in above
      point.
    - Smack: Add a comment above init_smk_fs explaining why we
      can't initialize smackfs under the security_init context.
    - mmm, Will we reach v10 ?
]

-->

Add the security= boot parameter. This is done to avoid LSM 
registration clashes in case of more than one bult-in module.

User can choose a security module to enable at boot. If no 
security= boot parameter is specified, only the first LSM 
asking for registration will be loaded. An invalid security 
module name will be treated as if no module has been chosen.

LSM modules must check now if they are allowed to register
by calling security_module_enable(ops) first. Modify SELinux 
and SMACK to do so.

Do not let SMACK register smackfs if it was not chosen on
boot. Smackfs assumes that smack hooks are registered and
the initial task security setup (swapper->security) is done.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
Reported-by: Alexey Dobriyan <adobriyan@sw.ru>
--- 

 Documentation/kernel-parameters.txt |    6 ++++
 include/linux/security.h            |   12 +++++++++
 security/dummy.c                    |    2 -
 security/security.c                 |   46 +++++++++++++++++++++++++++++++++++-
 security/selinux/hooks.c            |    7 +++++
 security/smack/smack.h              |    2 +
 security/smack/smack_lsm.c          |    7 ++++-
 security/smack/smackfs.c            |   11 +++++++-

 8 files changed, 89 insertions(+), 4 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9a5b665..64efbdc 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -374,6 +374,12 @@ and is between 256 and 4096 characters. It is defined in the file
 			possible to determine what the correct size should be.
 			This option provides an override for these situations.
 
+	security=	[SECURITY] Choose a security module to enable at boot. 
+			If this boot parameter is not specified, only the first 
+			security module asking for security registration will be
+			loaded. An invalid security module name will be treated
+			as if no module has been chosen.
+
 	capability.disable=
 			[SECURITY] Disable capabilities.  This would normally
 			be used only if an alternative security model is to be
diff --git a/include/linux/security.h b/include/linux/security.h
index fe52cde..801c9ad 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -42,6 +42,9 @@
 
 extern unsigned securebits;
 
+/* Maximum number of letters for an LSM name string */
+#define SECURITY_NAME_MAX	10
+
 struct ctl_table;
 
 /*
@@ -117,6 +120,12 @@ struct request_sock;
 /**
  * struct security_operations - main security structure
  *
+ * Security module identifier.
+ *
+ * @name:
+ *	A string that acts as a unique identifeir for the LSM with max number
+ *	of characters = SECURITY_NAME_MAX.
+ *
  * Security hooks for program execution operations.
  *
  * @bprm_alloc_security:
@@ -1207,6 +1216,8 @@ struct request_sock;
  * This is the main security structure.
  */
 struct security_operations {
+	char name[SECURITY_NAME_MAX + 1];
+
 	int (*ptrace) (struct task_struct * parent, struct task_struct * child);
 	int (*capget) (struct task_struct * target,
 		       kernel_cap_t * effective,
@@ -1466,6 +1477,7 @@ struct security_operations {
 
 /* prototypes */
 extern int security_init	(void);
+extern int security_module_enable(struct security_operations *ops);
 extern int register_security	(struct security_operations *ops);
 extern int mod_reg_security	(const char *name, struct security_operations *ops);
 extern struct dentry *securityfs_create_file(const char *name, mode_t mode,
diff --git a/security/dummy.c b/security/dummy.c
index 649326b..96d196f 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -979,7 +979,7 @@ static inline int dummy_key_permission(key_ref_t key_ref,
 }
 #endif /* CONFIG_KEYS */
 
-struct security_operations dummy_security_ops;
+struct security_operations dummy_security_ops = { "dummy" };
 
 #define set_to_dummy_if_null(ops, function)				\
 	do {								\
diff --git a/security/security.c b/security/security.c
index d15e56c..deb7e00 100644
--- a/security/security.c
+++ b/security/security.c
@@ -17,6 +17,9 @@
 #include <linux/kernel.h>
 #include <linux/security.h>
 
+/* Boot-time LSM user choice */
+static spinlock_t chosen_lsm_lock;
+static char chosen_lsm[SECURITY_NAME_MAX + 1];
 
 /* things that live in dummy.c */
 extern struct security_operations dummy_security_ops;
@@ -62,18 +65,59 @@ int __init security_init(void)
 	}
 
 	security_ops = &dummy_security_ops;
+	spin_lock_init(&chosen_lsm_lock);
 	do_security_initcalls();
 
 	return 0;
 }
 
+/* Save user chosen LSM */
+static int __init choose_lsm(char *str)
+{
+	strncpy(chosen_lsm, str, SECURITY_NAME_MAX);
+	return 1;
+}
+__setup("security=", choose_lsm);
+
+/**
+ * security_module_enable - Load given security module on boot ?
+ * @ops: a pointer to the struct security_operations that is to be checked.
+ *
+ * Each LSM must pass this method before registering its own operations
+ * to avoid security registration races. This method may also be used
+ * to check if your LSM is currently loaded.
+ *
+ * Return true if:
+ *	-The passed LSM is the one chosen by user at boot time,
+ *	-or user didsn't specify a specific LSM and we're the first to ask
+ *	 for registeration permissoin,
+ *	-or the passed LSM is currently loaded.
+ * Otherwise, return false.
+ */
+int security_module_enable(struct security_operations *ops)
+{
+	int rc = 1;
+
+	spin_lock(&chosen_lsm_lock);
+
+	if (!*chosen_lsm)
+		strncpy(chosen_lsm, ops->name, SECURITY_NAME_MAX);
+	else if (strncmp(ops->name, chosen_lsm, SECURITY_NAME_MAX))
+		rc = 0;
+
+	spin_unlock(&chosen_lsm_lock);
+
+	return rc;
+}
+
 /**
  * register_security - registers a security framework with the kernel
  * @ops: a pointer to the struct security_options that is to be registered
  *
  * This function is to allow a security module to register itself with the
  * kernel security subsystem.  Some rudimentary checking is done on the @ops
- * value passed to this function.
+ * value passed to this function. You'll need to check first if your LSM
+ * is allowed to register its @ops by calling security_module_enable(@ops).
  *
  * If there is already a security module registered with the kernel,
  * an error will be returned.  Otherwise 0 is returned on success.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 75c2e99..49709a4 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5219,6 +5219,8 @@ static int selinux_key_permission(key_ref_t key_ref,
 #endif
 
 static struct security_operations selinux_ops = {
+	.name =				"selinux",
+
 	.ptrace =			selinux_ptrace,
 	.capget =			selinux_capget,
 	.capset_check =			selinux_capset_check,
@@ -5405,6 +5407,11 @@ static __init int selinux_init(void)
 {
 	struct task_security_struct *tsec;
 
+	if (!security_module_enable(&selinux_ops)) {
+		selinux_enabled = 0;
+		return 0;
+	}
+
 	if (!selinux_enabled) {
 		printk(KERN_INFO "SELinux:  Disabled at boot.\n");
 		return 0;
diff --git a/security/smack/smack.h b/security/smack/smack.h
index a21a0e9..c444f48 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -15,6 +15,7 @@
 
 #include <linux/capability.h>
 #include <linux/spinlock.h>
+#include <linux/security.h>
 #include <net/netlabel.h>
 
 /*
@@ -195,6 +196,7 @@ extern struct smack_known smack_known_star;
 extern struct smack_known smack_known_unset;
 
 extern struct smk_list_entry *smack_list;
+extern struct security_operations smack_ops;
 
 /*
  * Stricly for CIPSO level manipulation.
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 770eb06..afa7967 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -2433,7 +2433,9 @@ static void smack_release_secctx(char *secdata, u32 seclen)
 {
 }
 
-static struct security_operations smack_ops = {
+struct security_operations smack_ops = {
+	.name =				"smack",
+
 	.ptrace = 			smack_ptrace,
 	.capget = 			cap_capget,
 	.capset_check = 		cap_capset_check,
@@ -2566,6 +2568,9 @@ static struct security_operations smack_ops = {
  */
 static __init int smack_init(void)
 {
+	if (!security_module_enable(&smack_ops))
+		return 0;
+
 	printk(KERN_INFO "Smack:  Initializing.\n");
 
 	/*
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 358c92c..effd3de 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -986,12 +986,21 @@ static struct vfsmount *smackfs_mount;
  *
  * register the smackfs
  *
- * Returns 0 unless the registration fails.
+ * Do not register smackfs if Smack wasn't enabled
+ * on boot. We can not put this method normally under the
+ * smack_init() code path since the security subsystem get
+ * initialized before the vfs caches.
+ *
+ * Returns true if we were not chosen on boot or if
+ * we were chosen and filesystem registration succeeded.
  */
 static int __init init_smk_fs(void)
 {
 	int err;
 
+	if (!security_module_enable(&smack_ops))
+		return 0;
+
 	err = register_filesystem(&smk_fs_type);
 	if (!err) {
 		smackfs_mount = kern_mount(&smk_fs_type);

--
"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com

Re: [PATCH BUGFIX -rc3] Smack: Don't register smackfs if we're not loaded

[Linus Torvalds]

On Tue, 4 Mar 2008, Ahmed S. Darwish wrote:
> 
> Smackfs initialization without an enabled Smack leads to
> an early Oops that renders the system unusable.

I really think this is bogus. Global enables like this are just wrong, and 
a sign that something else bad is going on.

What is the oops? Why does it happen?

		Linus

Re: [PATCH BUGFIX -rc3] Smack: Don't register smackfs if we're not loaded

[Ahmed S. Darwish]

Hi Linus,

[Adding SELinux devs to CC list, please follow to the SELinux point.]

On Tue, Mar 04, 2008 at 09:21:19AM -0800, Linus Torvalds wrote:
> 
> 
> On Tue, 4 Mar 2008, Ahmed S. Darwish wrote:
> > 
> > Smackfs initialization without an enabled Smack leads to
> > an early Oops that renders the system unusable.
> 
> I really think this is bogus. Global enables like this are just wrong, and 
> a sign that something else bad is going on.
> 
> What is the oops? Why does it happen?
> 

The problem occurs when Smack is built-in the kernel but not chosen
to register itself on boot. Smack was not chosen on boot cause either
security=AnotherLSM or security=NonExistentLSM.

In all cases, init_smk_fs() ,which registers smackfs, got called
cause it's an __initcall(init_smack_fs). 
This include the cases where smack __was not__ chosen on boot.

Making smackfs mountable when Smack is not registered leads to:

1- an Oops by dereferncing the NULL security pointer: current->security (*)

2- Smackfs code got executed though naturally all the code assumes
   that smack is already registered with the security system leading
   to several problems.

3- The bogus idea of having a subsystem interface available when the
   subsystem itself is not available!

So the global is used in init_smk_fs to not register smackfs if
Smack wasn't enabled on boot.

---- SELinux:

I think the SELinux folks faced the same problem too. In my first 
local iteration of the security= parameter patch, I forgot to set 
`selinux_disable = 1' if SELinux wasn't chosen on boot.

This led to dozen of SELinux Udev events and also led to selinuxfs 
being available even though SELinux hooks _weren't_ registered.

Regards,

(*) 
    Could not save the oops cause it occured too early, but
    it was like this:

    __init_call
    init_smk_fs(void)
    smk_unlbl_ambient(NULL)
    /* 
     * Here: current->security = NULL, cause SMACK initial setup
     * was not executed.
     */
    smack_to_secid(current->security) 
    strncmp(.., current->security, ..) 
    
-- 

"Better to light a candle, than curse the darkness"

Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com