Re: [PATCH v4 1/3] LSM: Add /sys/kernel/security/lsm

[Paul Moore <paul@paul-moore.com>]

On Thu, Jun 23, 2016 at 5:10 PM, Casey Schaufler <casey@schaufler-ca.com> wrote:
> Subject: [PATCH v4 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        | 38 ++++++++++++++++++++++++++++++++++++++
>  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, 75 insertions(+), 17 deletions(-)

Seems reasonable to me.

Acked-by: Paul Moore <paul@paul-moore.com>

> 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..1093f73 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 +79,22 @@ 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 = kasprintf(GFP_KERNEL, "%s,%s", *result, new);
> +               if (cp == NULL)
> +                       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 +114,27 @@ 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();
>  }
>



-- 
paul moore
www.paul-moore.com