LSM: Switch to lists of hooks

Instead of using a vector of security operations
with explicit, special case stacking of the capability
and yama hooks use lists of hooks with capability and
yama hooks included as appropriate.

The security_operations structure is no longer required.
Instead, there is a union of the function pointers that
allows all the hooks lists to use a common mechanism for
list management while retaining typing. Each module
supplies an array describing the hooks it provides instead
of a sparsely populated security_operations structure.
The description includes the element that gets put on
the hook list, avoiding the issues surrounding individual
element allocation.

The method for registering security modules is changed to
reflect the information available. The method for removing
a module, currently only used by SELinux, has also changed.
It should be generic now, however if there are potential
race conditions based on ordering of hook removal that needs
to be addressed by the calling module.

The security hooks are called from the lists and the first
failure is returned.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <james.l.morris@oracle.com>

2 files changed, 18 insertions, 45 deletions

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index d97cba3e3849..dc0027b28b04 100644
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -347,9 +347,7 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
                 file_inode(bprm->file)->i_mode
         };
         const char *name = NULL, *target = NULL, *info = NULL;
-        int error = cap_bprm_set_creds(bprm);
-        if (error)
-                return error;
+        int error = 0;
 
         if (bprm->cred_prepared)
                 return 0;
@@ -531,15 +529,13 @@ cleanup:
  */
 int apparmor_bprm_secureexec(struct linux_binprm *bprm)
 {
-        int ret = cap_bprm_secureexec(bprm);
-
         /* the decision to use secure exec is computed in set_creds
          * and stored in bprm->unsafe.
          */
-        if (!ret && (bprm->unsafe & AA_SECURE_X_NEEDED))
-                ret = 1;
+        if (bprm->unsafe & AA_SECURE_X_NEEDED)
+                return 1;
 
-        return ret;
+        return 0;
 }
 
 /**
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index f54253258fb8..5696874e8062 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -96,19 +96,11 @@ static void apparmor_cred_transfer(struct cred *new, const struct cred *old)
 static int apparmor_ptrace_access_check(struct task_struct *child,
                                         unsigned int mode)
 {
-        int error = cap_ptrace_access_check(child, mode);
-        if (error)
-                return error;
-
         return aa_ptrace(current, child, mode);
 }
 
 static int apparmor_ptrace_traceme(struct task_struct *parent)
 {
-        int error = cap_ptrace_traceme(parent);
-        if (error)
-                return error;
-
         return aa_ptrace(parent, current, PTRACE_MODE_ATTACH);
 }
 
@@ -123,10 +115,10 @@ static int apparmor_capget(struct task_struct *target, kernel_cap_t *effective,
         cred = __task_cred(target);
         profile = aa_cred_profile(cred);
 
-        *effective = cred->cap_effective;
-        *inheritable = cred->cap_inheritable;
-        *permitted = cred->cap_permitted;
-
+        /*
+         * cap_capget is stacked ahead of this and will
+         * initialize effective and permitted.
+         */
         if (!unconfined(profile) && !COMPLAIN_MODE(profile)) {
                 *effective = cap_intersect(*effective, profile->caps.allow);
                 *permitted = cap_intersect(*permitted, profile->caps.allow);
@@ -140,13 +132,11 @@ static int apparmor_capable(const struct cred *cred, struct user_namespace *ns,
                             int cap, int audit)
 {
         struct aa_profile *profile;
-        /* cap_capable returns 0 on success, else -EPERM */
-        int error = cap_capable(cred, ns, cap, audit);
-        if (!error) {
-                profile = aa_cred_profile(cred);
-                if (!unconfined(profile))
-                        error = aa_capable(profile, cap, audit);
-        }
+        int error = 0;
+
+        profile = aa_cred_profile(cred);
+        if (!unconfined(profile))
+                error = aa_capable(profile, cap, audit);
         return error;
 }
 
@@ -615,9 +605,7 @@ static int apparmor_task_setrlimit(struct task_struct *task,
         return error;
 }
 
-static struct security_operations apparmor_ops = {
-        LSM_HOOK_INIT(name, "apparmor"),
-
+static struct security_hook_list apparmor_hooks[] = {
         LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
         LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
         LSM_HOOK_INIT(capget, apparmor_capget),
@@ -640,7 +628,6 @@ static struct security_operations apparmor_ops = {
         LSM_HOOK_INIT(file_alloc_security, apparmor_file_alloc_security),
         LSM_HOOK_INIT(file_free_security, apparmor_file_free_security),
         LSM_HOOK_INIT(mmap_file, apparmor_mmap_file),
-        LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
         LSM_HOOK_INIT(file_mprotect, apparmor_file_mprotect),
         LSM_HOOK_INIT(file_lock, apparmor_file_lock),
 
@@ -898,7 +885,7 @@ static int __init apparmor_init(void)
 {
         int error;
 
-        if (!apparmor_enabled || !security_module_enable(&apparmor_ops)) {
+        if (!apparmor_enabled || !security_module_enable("apparmor")) {
                 aa_info_message("AppArmor disabled by boot time parameter");
                 apparmor_enabled = 0;
                 return 0;
@@ -913,17 +900,10 @@ static int __init apparmor_init(void)
         error = set_init_cxt();
         if (error) {
                 AA_ERROR("Failed to set context on init task\n");
-                goto register_security_out;
-        }
-
-        error = register_security(&apparmor_ops);
-        if (error) {
-                struct cred *cred = (struct cred *)current->real_cred;
-                aa_free_task_context(cred_cxt(cred));
-                cred_cxt(cred) = NULL;
-                AA_ERROR("Unable to register AppArmor\n");
-                goto register_security_out;
+                aa_free_root_ns();
+                goto alloc_out;
         }
+        security_add_hooks(apparmor_hooks, ARRAY_SIZE(apparmor_hooks));
 
         /* Report that AppArmor successfully initialized */
         apparmor_initialized = 1;
@@ -936,9 +916,6 @@ static int __init apparmor_init(void)
 
         return error;
 
-register_security_out:
-        aa_free_root_ns();
-
 alloc_out:
         aa_destroy_aafs();