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[PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm

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  [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm Casey Schaufler <casey@schaufler-ca.com> - 2016-06-10 23:30 +0200
    Re: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm Kees Cook <keescook@chromium.org> - 2016-06-14 20:50 +0200
      Re: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm Casey Schaufler <casey@schaufler-ca.com> - 2016-06-14 21:40 +0200
    Re: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm "David A. Wheeler" <dwheeler@dwheeler.com> - 2016-06-15 00:50 +0200

#1419734 — [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm

Subject: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm

I got tired of having to find indirect ways to
determine what security modules are active on a system.
I have added /sys/kernel/security/lsm, which contains a
comma separated list of the active security modules. No
more groping around in /proc/filesystems, which won't
help if the module doesn't support its own filesystem.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

---
 include/linux/lsm_hooks.h  | 12 ++++--------
 security/apparmor/lsm.c    |  3 ++-
 security/commoncap.c       |  3 ++-
 security/inode.c           | 26 ++++++++++++++++++++++++--
 security/loadpin/loadpin.c |  2 +-
 security/security.c        | 39 +++++++++++++++++++++++++++++++++++++++
 security/selinux/hooks.c   |  2 +-
 security/smack/smack_lsm.c |  2 +-
 security/tomoyo/tomoyo.c   |  2 +-
 security/yama/yama_lsm.c   |  2 +-
 10 files changed, 76 insertions(+), 17 deletions(-)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 7ae3976..0bfd441 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1841,6 +1841,7 @@ struct security_hook_list {
 	struct list_head		list;
 	struct list_head		*head;
 	union security_list_options	hook;
+	char				*lsm;
 };
 
 /*
@@ -1853,15 +1854,10 @@ struct security_hook_list {
 	{ .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
 
 extern struct security_hook_heads security_hook_heads;
+extern char *lsm_names;
 
-static inline void security_add_hooks(struct security_hook_list *hooks,
-				      int count)
-{
-	int i;
-
-	for (i = 0; i < count; i++)
-		list_add_tail_rcu(&hooks[i].list, hooks[i].head);
-}
+extern void security_add_hooks(struct security_hook_list *hooks, int count,
+				char *lsm);
 
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 /*
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 2660fbc..fb0fb03 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -880,7 +880,8 @@ static int __init apparmor_init(void)
 		aa_free_root_ns();
 		goto alloc_out;
 	}
-	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks));
+	security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
+				"apparmor");
 
 	/* Report that AppArmor successfully initialized */
 	apparmor_initialized = 1;
diff --git a/security/commoncap.c b/security/commoncap.c
index e7fadde..d101734 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -1090,7 +1090,8 @@ struct security_hook_list capability_hooks[] = {
 
 void __init capability_add_hooks(void)
 {
-	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
+	security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
+				"capability");
 }
 
 #endif /* CONFIG_SECURITY */
diff --git a/security/inode.c b/security/inode.c
index 28414b0..235ad82 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -20,6 +20,7 @@
 #include <linux/init.h>
 #include <linux/namei.h>
 #include <linux/security.h>
+#include <linux/lsm_hooks.h>
 #include <linux/magic.h>
 
 static struct vfsmount *mount;
@@ -208,6 +209,21 @@ void securityfs_remove(struct dentry *dentry)
 }
 EXPORT_SYMBOL_GPL(securityfs_remove);
 
+#ifdef CONFIG_SECURITY
+static struct dentry *lsm_dentry;
+static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
+			loff_t *ppos)
+{
+	return simple_read_from_buffer(buf, count, ppos, lsm_names,
+		strlen(lsm_names));
+}
+
+static const struct file_operations lsm_ops = {
+	.read = lsm_read,
+	.llseek = generic_file_llseek,
+};
+#endif
+
 static int __init securityfs_init(void)
 {
 	int retval;
@@ -217,9 +233,15 @@ static int __init securityfs_init(void)
 		return retval;
 
 	retval = register_filesystem(&fs_type);
-	if (retval)
+	if (retval) {
 		sysfs_remove_mount_point(kernel_kobj, "security");
-	return retval;
+		return retval;
+	}
+#ifdef CONFIG_SECURITY
+	lsm_dentry = securityfs_create_file("lsm", S_IRUGO, NULL, NULL,
+						&lsm_ops);
+#endif
+	return 0;
 }
 
 core_initcall(securityfs_init);
diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
index 89a46f1..1d82eae 100644
--- a/security/loadpin/loadpin.c
+++ b/security/loadpin/loadpin.c
@@ -182,7 +182,7 @@ static struct security_hook_list loadpin_hooks[] = {
 void __init loadpin_add_hooks(void)
 {
 	pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
-	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks));
+	security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
 }
 
 /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
diff --git a/security/security.c b/security/security.c
index c4bb47d..dd792d5 100644
--- a/security/security.c
+++ b/security/security.c
@@ -32,6 +32,7 @@
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
 
+char *lsm_names;
 /* Boot-time LSM user choice */
 static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
 	CONFIG_DEFAULT_SECURITY;
@@ -78,6 +79,23 @@ static int __init choose_lsm(char *str)
 }
 __setup("security=", choose_lsm);
 
+static int lsm_append(char *new, char **result)
+{
+	char *cp;
+
+	if (*result == NULL) {
+		*result = kstrdup(new, GFP_KERNEL);
+	} else {
+		cp = kzalloc(strlen(*result) + strlen(new) + 2, GFP_KERNEL);
+		if (cp == NULL)
+			return -ENOMEM;
+		sprintf(cp, "%s,%s", *result, new);
+		kfree(*result);
+		*result = cp;
+	}
+	return 0;
+}
+
 /**
  * security_module_enable - Load given security module on boot ?
  * @module: the name of the module
@@ -97,6 +115,27 @@ int __init security_module_enable(const char *module)
 	return !strcmp(module, chosen_lsm);
 }
 
+/**
+ * security_add_hooks - Add a modules hooks to the hook lists.
+ * @hooks: the hooks to add
+ * @count: the number of hooks to add
+ * @lsm: the name of the security module
+ *
+ * Each LSM has to register its hooks with the infrastructure.
+ */
+void __init security_add_hooks(struct security_hook_list *hooks, int count,
+				char *lsm)
+{
+	int i;
+
+	for (i = 0; i < count; i++) {
+		hooks[i].lsm = lsm;
+		list_add_tail_rcu(&hooks[i].list, hooks[i].head);
+	}
+	if (lsm_append(lsm, &lsm_names) < 0)
+		panic("%s - Cannot get early memory.\n", __func__);
+}
+
 /*
  * Hook list operation macros.
  *
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a86d537..ed3a757 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6233,7 +6233,7 @@ static __init int selinux_init(void)
 					    0, SLAB_PANIC, NULL);
 	avc_init();
 
-	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks));
+	security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
 
 	if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
 		panic("SELinux: Unable to register AVC netcache callback\n");
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6777295..3577009 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -4801,7 +4801,7 @@ static __init int smack_init(void)
 	/*
 	 * Register with LSM
 	 */
-	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks));
+	security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
 
 	return 0;
 }
diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
index 75c9987..edc52d6 100644
--- a/security/tomoyo/tomoyo.c
+++ b/security/tomoyo/tomoyo.c
@@ -542,7 +542,7 @@ static int __init tomoyo_init(void)
 	if (!security_module_enable("tomoyo"))
 		return 0;
 	/* register ourselves with the security framework */
-	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks));
+	security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
 	printk(KERN_INFO "TOMOYO Linux initialized\n");
 	cred->security = &tomoyo_kernel_domain;
 	tomoyo_mm_init();
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index 0309f21..f8ee60e 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -471,6 +471,6 @@ static inline void yama_init_sysctl(void) { }
 void __init yama_add_hooks(void)
 {
 	pr_info("Yama: becoming mindful.\n");
-	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
+	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
 	yama_init_sysctl();
 }

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#1422214

On Fri, Jun 10, 2016 at 2:25 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
> Subject: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm
>
> I got tired of having to find indirect ways to
> determine what security modules are active on a system.
> I have added /sys/kernel/security/lsm, which contains a
> comma separated list of the active security modules. No
> more groping around in /proc/filesystems, which won't
> help if the module doesn't support its own filesystem.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

Looks good to me. I might tweak the copy code below, but otherwise:

Acked-by: Kees Cook <keescook@chromium.org>

>
> ---
>  include/linux/lsm_hooks.h  | 12 ++++--------
>  security/apparmor/lsm.c    |  3 ++-
>  security/commoncap.c       |  3 ++-
>  security/inode.c           | 26 ++++++++++++++++++++++++--
>  security/loadpin/loadpin.c |  2 +-
>  security/security.c        | 39 +++++++++++++++++++++++++++++++++++++++
>  security/selinux/hooks.c   |  2 +-
>  security/smack/smack_lsm.c |  2 +-
>  security/tomoyo/tomoyo.c   |  2 +-
>  security/yama/yama_lsm.c   |  2 +-
>  10 files changed, 76 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 7ae3976..0bfd441 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1841,6 +1841,7 @@ struct security_hook_list {
>         struct list_head                list;
>         struct list_head                *head;
>         union security_list_options     hook;
> +       char                            *lsm;
>  };
>
>  /*
> @@ -1853,15 +1854,10 @@ struct security_hook_list {
>         { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
>
>  extern struct security_hook_heads security_hook_heads;
> +extern char *lsm_names;
>
> -static inline void security_add_hooks(struct security_hook_list *hooks,
> -                                     int count)
> -{
> -       int i;
> -
> -       for (i = 0; i < count; i++)
> -               list_add_tail_rcu(&hooks[i].list, hooks[i].head);
> -}
> +extern void security_add_hooks(struct security_hook_list *hooks, int count,
> +                               char *lsm);
>
>  #ifdef CONFIG_SECURITY_SELINUX_DISABLE
>  /*
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 2660fbc..fb0fb03 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -880,7 +880,8 @@ static int __init apparmor_init(void)
>                 aa_free_root_ns();
>                 goto alloc_out;
>         }
> -       security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks));
> +       security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
> +                               "apparmor");
>
>         /* Report that AppArmor successfully initialized */
>         apparmor_initialized = 1;
> diff --git a/security/commoncap.c b/security/commoncap.c
> index e7fadde..d101734 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -1090,7 +1090,8 @@ struct security_hook_list capability_hooks[] = {
>
>  void __init capability_add_hooks(void)
>  {
> -       security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
> +       security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
> +                               "capability");
>  }
>
>  #endif /* CONFIG_SECURITY */
> diff --git a/security/inode.c b/security/inode.c
> index 28414b0..235ad82 100644
> --- a/security/inode.c
> +++ b/security/inode.c
> @@ -20,6 +20,7 @@
>  #include <linux/init.h>
>  #include <linux/namei.h>
>  #include <linux/security.h>
> +#include <linux/lsm_hooks.h>
>  #include <linux/magic.h>
>
>  static struct vfsmount *mount;
> @@ -208,6 +209,21 @@ void securityfs_remove(struct dentry *dentry)
>  }
>  EXPORT_SYMBOL_GPL(securityfs_remove);
>
> +#ifdef CONFIG_SECURITY
> +static struct dentry *lsm_dentry;
> +static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
> +                       loff_t *ppos)
> +{
> +       return simple_read_from_buffer(buf, count, ppos, lsm_names,
> +               strlen(lsm_names));
> +}
> +
> +static const struct file_operations lsm_ops = {
> +       .read = lsm_read,
> +       .llseek = generic_file_llseek,
> +};
> +#endif
> +
>  static int __init securityfs_init(void)
>  {
>         int retval;
> @@ -217,9 +233,15 @@ static int __init securityfs_init(void)
>                 return retval;
>
>         retval = register_filesystem(&fs_type);
> -       if (retval)
> +       if (retval) {
>                 sysfs_remove_mount_point(kernel_kobj, "security");
> -       return retval;
> +               return retval;
> +       }
> +#ifdef CONFIG_SECURITY
> +       lsm_dentry = securityfs_create_file("lsm", S_IRUGO, NULL, NULL,
> +                                               &lsm_ops);
> +#endif
> +       return 0;
>  }
>
>  core_initcall(securityfs_init);
> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
> index 89a46f1..1d82eae 100644
> --- a/security/loadpin/loadpin.c
> +++ b/security/loadpin/loadpin.c
> @@ -182,7 +182,7 @@ static struct security_hook_list loadpin_hooks[] = {
>  void __init loadpin_add_hooks(void)
>  {
>         pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
> -       security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks));
> +       security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
>  }
>
>  /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
> diff --git a/security/security.c b/security/security.c
> index c4bb47d..dd792d5 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -32,6 +32,7 @@
>  /* Maximum number of letters for an LSM name string */
>  #define SECURITY_NAME_MAX      10
>
> +char *lsm_names;
>  /* Boot-time LSM user choice */
>  static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
>         CONFIG_DEFAULT_SECURITY;
> @@ -78,6 +79,23 @@ static int __init choose_lsm(char *str)
>  }
>  __setup("security=", choose_lsm);
>
> +static int lsm_append(char *new, char **result)
> +{
> +       char *cp;
> +
> +       if (*result == NULL) {
> +               *result = kstrdup(new, GFP_KERNEL);
> +       } else {
> +               cp = kzalloc(strlen(*result) + strlen(new) + 2, GFP_KERNEL);
> +               if (cp == NULL)
> +                       return -ENOMEM;
> +               sprintf(cp, "%s,%s", *result, new);

Instead of the kzalloc+sprintf, this could be:

cp = kasprintf(GFP_KERNEL, "%s,%s", *result, new);
if (!cp)
    return -ENOMEM;


> +               kfree(*result);
> +               *result = cp;
> +       }
> +       return 0;
> +}
> +
>  /**
>   * security_module_enable - Load given security module on boot ?
>   * @module: the name of the module
> @@ -97,6 +115,27 @@ int __init security_module_enable(const char *module)
>         return !strcmp(module, chosen_lsm);
>  }
>
> +/**
> + * security_add_hooks - Add a modules hooks to the hook lists.
> + * @hooks: the hooks to add
> + * @count: the number of hooks to add
> + * @lsm: the name of the security module
> + *
> + * Each LSM has to register its hooks with the infrastructure.
> + */
> +void __init security_add_hooks(struct security_hook_list *hooks, int count,
> +                               char *lsm)
> +{
> +       int i;
> +
> +       for (i = 0; i < count; i++) {
> +               hooks[i].lsm = lsm;
> +               list_add_tail_rcu(&hooks[i].list, hooks[i].head);
> +       }
> +       if (lsm_append(lsm, &lsm_names) < 0)
> +               panic("%s - Cannot get early memory.\n", __func__);
> +}
> +
>  /*
>   * Hook list operation macros.
>   *
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index a86d537..ed3a757 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -6233,7 +6233,7 @@ static __init int selinux_init(void)
>                                             0, SLAB_PANIC, NULL);
>         avc_init();
>
> -       security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks));
> +       security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
>
>         if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
>                 panic("SELinux: Unable to register AVC netcache callback\n");
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 6777295..3577009 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4801,7 +4801,7 @@ static __init int smack_init(void)
>         /*
>          * Register with LSM
>          */
> -       security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks));
> +       security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
>
>         return 0;
>  }
> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
> index 75c9987..edc52d6 100644
> --- a/security/tomoyo/tomoyo.c
> +++ b/security/tomoyo/tomoyo.c
> @@ -542,7 +542,7 @@ static int __init tomoyo_init(void)
>         if (!security_module_enable("tomoyo"))
>                 return 0;
>         /* register ourselves with the security framework */
> -       security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks));
> +       security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
>         printk(KERN_INFO "TOMOYO Linux initialized\n");
>         cred->security = &tomoyo_kernel_domain;
>         tomoyo_mm_init();
> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
> index 0309f21..f8ee60e 100644
> --- a/security/yama/yama_lsm.c
> +++ b/security/yama/yama_lsm.c
> @@ -471,6 +471,6 @@ static inline void yama_init_sysctl(void) { }
>  void __init yama_add_hooks(void)
>  {
>         pr_info("Yama: becoming mindful.\n");
> -       security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
> +       security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
>         yama_init_sysctl();
>  }
>

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security

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#1422255

On 6/14/2016 11:41 AM, Kees Cook wrote:
> On Fri, Jun 10, 2016 at 2:25 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
>> Subject: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm
>>
>> I got tired of having to find indirect ways to
>> determine what security modules are active on a system.
>> I have added /sys/kernel/security/lsm, which contains a
>> comma separated list of the active security modules. No
>> more groping around in /proc/filesystems, which won't
>> help if the module doesn't support its own filesystem.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Looks good to me. I might tweak the copy code below, but otherwise:
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
>> ---
>>  include/linux/lsm_hooks.h  | 12 ++++--------
>>  security/apparmor/lsm.c    |  3 ++-
>>  security/commoncap.c       |  3 ++-
>>  security/inode.c           | 26 ++++++++++++++++++++++++--
>>  security/loadpin/loadpin.c |  2 +-
>>  security/security.c        | 39 +++++++++++++++++++++++++++++++++++++++
>>  security/selinux/hooks.c   |  2 +-
>>  security/smack/smack_lsm.c |  2 +-
>>  security/tomoyo/tomoyo.c   |  2 +-
>>  security/yama/yama_lsm.c   |  2 +-
>>  10 files changed, 76 insertions(+), 17 deletions(-)
>>
>> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
>> index 7ae3976..0bfd441 100644
>> --- a/include/linux/lsm_hooks.h
>> +++ b/include/linux/lsm_hooks.h
>> @@ -1841,6 +1841,7 @@ struct security_hook_list {
>>         struct list_head                list;
>>         struct list_head                *head;
>>         union security_list_options     hook;
>> +       char                            *lsm;
>>  };
>>
>>  /*
>> @@ -1853,15 +1854,10 @@ struct security_hook_list {
>>         { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
>>
>>  extern struct security_hook_heads security_hook_heads;
>> +extern char *lsm_names;
>>
>> -static inline void security_add_hooks(struct security_hook_list *hooks,
>> -                                     int count)
>> -{
>> -       int i;
>> -
>> -       for (i = 0; i < count; i++)
>> -               list_add_tail_rcu(&hooks[i].list, hooks[i].head);
>> -}
>> +extern void security_add_hooks(struct security_hook_list *hooks, int count,
>> +                               char *lsm);
>>
>>  #ifdef CONFIG_SECURITY_SELINUX_DISABLE
>>  /*
>> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
>> index 2660fbc..fb0fb03 100644
>> --- a/security/apparmor/lsm.c
>> +++ b/security/apparmor/lsm.c
>> @@ -880,7 +880,8 @@ static int __init apparmor_init(void)
>>                 aa_free_root_ns();
>>                 goto alloc_out;
>>         }
>> -       security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks));
>> +       security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks),
>> +                               "apparmor");
>>
>>         /* Report that AppArmor successfully initialized */
>>         apparmor_initialized = 1;
>> diff --git a/security/commoncap.c b/security/commoncap.c
>> index e7fadde..d101734 100644
>> --- a/security/commoncap.c
>> +++ b/security/commoncap.c
>> @@ -1090,7 +1090,8 @@ struct security_hook_list capability_hooks[] = {
>>
>>  void __init capability_add_hooks(void)
>>  {
>> -       security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks));
>> +       security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
>> +                               "capability");
>>  }
>>
>>  #endif /* CONFIG_SECURITY */
>> diff --git a/security/inode.c b/security/inode.c
>> index 28414b0..235ad82 100644
>> --- a/security/inode.c
>> +++ b/security/inode.c
>> @@ -20,6 +20,7 @@
>>  #include <linux/init.h>
>>  #include <linux/namei.h>
>>  #include <linux/security.h>
>> +#include <linux/lsm_hooks.h>
>>  #include <linux/magic.h>
>>
>>  static struct vfsmount *mount;
>> @@ -208,6 +209,21 @@ void securityfs_remove(struct dentry *dentry)
>>  }
>>  EXPORT_SYMBOL_GPL(securityfs_remove);
>>
>> +#ifdef CONFIG_SECURITY
>> +static struct dentry *lsm_dentry;
>> +static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
>> +                       loff_t *ppos)
>> +{
>> +       return simple_read_from_buffer(buf, count, ppos, lsm_names,
>> +               strlen(lsm_names));
>> +}
>> +
>> +static const struct file_operations lsm_ops = {
>> +       .read = lsm_read,
>> +       .llseek = generic_file_llseek,
>> +};
>> +#endif
>> +
>>  static int __init securityfs_init(void)
>>  {
>>         int retval;
>> @@ -217,9 +233,15 @@ static int __init securityfs_init(void)
>>                 return retval;
>>
>>         retval = register_filesystem(&fs_type);
>> -       if (retval)
>> +       if (retval) {
>>                 sysfs_remove_mount_point(kernel_kobj, "security");
>> -       return retval;
>> +               return retval;
>> +       }
>> +#ifdef CONFIG_SECURITY
>> +       lsm_dentry = securityfs_create_file("lsm", S_IRUGO, NULL, NULL,
>> +                                               &lsm_ops);
>> +#endif
>> +       return 0;
>>  }
>>
>>  core_initcall(securityfs_init);
>> diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c
>> index 89a46f1..1d82eae 100644
>> --- a/security/loadpin/loadpin.c
>> +++ b/security/loadpin/loadpin.c
>> @@ -182,7 +182,7 @@ static struct security_hook_list loadpin_hooks[] = {
>>  void __init loadpin_add_hooks(void)
>>  {
>>         pr_info("ready to pin (currently %sabled)", enabled ? "en" : "dis");
>> -       security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks));
>> +       security_add_hooks(loadpin_hooks, ARRAY_SIZE(loadpin_hooks), "loadpin");
>>  }
>>
>>  /* Should not be mutable after boot, so not listed in sysfs (perm == 0). */
>> diff --git a/security/security.c b/security/security.c
>> index c4bb47d..dd792d5 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -32,6 +32,7 @@
>>  /* Maximum number of letters for an LSM name string */
>>  #define SECURITY_NAME_MAX      10
>>
>> +char *lsm_names;
>>  /* Boot-time LSM user choice */
>>  static __initdata char chosen_lsm[SECURITY_NAME_MAX + 1] =
>>         CONFIG_DEFAULT_SECURITY;
>> @@ -78,6 +79,23 @@ static int __init choose_lsm(char *str)
>>  }
>>  __setup("security=", choose_lsm);
>>
>> +static int lsm_append(char *new, char **result)
>> +{
>> +       char *cp;
>> +
>> +       if (*result == NULL) {
>> +               *result = kstrdup(new, GFP_KERNEL);
>> +       } else {
>> +               cp = kzalloc(strlen(*result) + strlen(new) + 2, GFP_KERNEL);
>> +               if (cp == NULL)
>> +                       return -ENOMEM;
>> +               sprintf(cp, "%s,%s", *result, new);
> Instead of the kzalloc+sprintf, this could be:
>
> cp = kasprintf(GFP_KERNEL, "%s,%s", *result, new);
> if (!cp)
>     return -ENOMEM;

Great, I'll do it.

>
>> +               kfree(*result);
>> +               *result = cp;
>> +       }
>> +       return 0;
>> +}
>> +
>>  /**
>>   * security_module_enable - Load given security module on boot ?
>>   * @module: the name of the module
>> @@ -97,6 +115,27 @@ int __init security_module_enable(const char *module)
>>         return !strcmp(module, chosen_lsm);
>>  }
>>
>> +/**
>> + * security_add_hooks - Add a modules hooks to the hook lists.
>> + * @hooks: the hooks to add
>> + * @count: the number of hooks to add
>> + * @lsm: the name of the security module
>> + *
>> + * Each LSM has to register its hooks with the infrastructure.
>> + */
>> +void __init security_add_hooks(struct security_hook_list *hooks, int count,
>> +                               char *lsm)
>> +{
>> +       int i;
>> +
>> +       for (i = 0; i < count; i++) {
>> +               hooks[i].lsm = lsm;
>> +               list_add_tail_rcu(&hooks[i].list, hooks[i].head);
>> +       }
>> +       if (lsm_append(lsm, &lsm_names) < 0)
>> +               panic("%s - Cannot get early memory.\n", __func__);
>> +}
>> +
>>  /*
>>   * Hook list operation macros.
>>   *
>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
>> index a86d537..ed3a757 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -6233,7 +6233,7 @@ static __init int selinux_init(void)
>>                                             0, SLAB_PANIC, NULL);
>>         avc_init();
>>
>> -       security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks));
>> +       security_add_hooks(selinux_hooks, ARRAY_SIZE(selinux_hooks), "selinux");
>>
>>         if (avc_add_callback(selinux_netcache_avc_callback, AVC_CALLBACK_RESET))
>>                 panic("SELinux: Unable to register AVC netcache callback\n");
>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
>> index 6777295..3577009 100644
>> --- a/security/smack/smack_lsm.c
>> +++ b/security/smack/smack_lsm.c
>> @@ -4801,7 +4801,7 @@ static __init int smack_init(void)
>>         /*
>>          * Register with LSM
>>          */
>> -       security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks));
>> +       security_add_hooks(smack_hooks, ARRAY_SIZE(smack_hooks), "smack");
>>
>>         return 0;
>>  }
>> diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c
>> index 75c9987..edc52d6 100644
>> --- a/security/tomoyo/tomoyo.c
>> +++ b/security/tomoyo/tomoyo.c
>> @@ -542,7 +542,7 @@ static int __init tomoyo_init(void)
>>         if (!security_module_enable("tomoyo"))
>>                 return 0;
>>         /* register ourselves with the security framework */
>> -       security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks));
>> +       security_add_hooks(tomoyo_hooks, ARRAY_SIZE(tomoyo_hooks), "tomoyo");
>>         printk(KERN_INFO "TOMOYO Linux initialized\n");
>>         cred->security = &tomoyo_kernel_domain;
>>         tomoyo_mm_init();
>> diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
>> index 0309f21..f8ee60e 100644
>> --- a/security/yama/yama_lsm.c
>> +++ b/security/yama/yama_lsm.c
>> @@ -471,6 +471,6 @@ static inline void yama_init_sysctl(void) { }
>>  void __init yama_add_hooks(void)
>>  {
>>         pr_info("Yama: becoming mindful.\n");
>> -       security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
>> +       security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks), "yama");
>>         yama_init_sysctl();
>>  }
>>
> -Kees
>

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#1422424

On Fri, 10 Jun 2016 14:25:45 -0700, Casey Schaufler <casey@schaufler-ca.com> wrote:
> Subject: [PATCH v3 1/3] LSM: Add /sys/kernel/security/lsm
> I got tired of having to find indirect ways to
> determine what security modules are active on a system.
> I have added /sys/kernel/security/lsm, which contains a
> comma separated list of the active security modules. No
> more groping around in /proc/filesystems, which won't
> help if the module doesn't support its own filesystem.

Great idea, thanks for doing it.

--- David A. Wheeler

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