capabilities: remove the task from capable LSM hook entirely

The capabilities framework is based around credentials, not necessarily the
current task.  Yet we still passed the current task down into LSMs from the
security_capable() LSM hook as if it was a meaningful portion of the security
decision.  This patch removes the 'generic' passing of current and instead
forces individual LSMs to use current explicitly if they think it is
appropriate.  In our case those LSMs are SELinux and AppArmor.

I believe the AppArmor use of current is incorrect, but that is wholely
unrelated to this patch.  This patch does not change what AppArmor does, it
just makes it clear in the AppArmor code that it is doing it.

The SELinux code still uses current in it's audit message, which may also be
wrong and needs further investigation.  Again this is NOT a change, it may
have always been wrong, this patch just makes it clear what is happening.

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 7 insertions, 9 deletions

diff --git a/include/linux/security.h b/include/linux/security.h
index ebd2a53a3d07..4921163b2752 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -53,8 +53,8 @@ struct user_namespace;
  * These functions are in security/capability.c and are used
  * as the default capabilities functions
  */
-extern int cap_capable(struct task_struct *tsk, const struct cred *cred,
-                       struct user_namespace *ns, int cap, int audit);
+extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
+                       int cap, int audit);
 extern int cap_settime(const struct timespec *ts, const struct timezone *tz);
 extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
 extern int cap_ptrace_traceme(struct task_struct *parent);
@@ -1261,7 +1261,6 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  * @capable:
  *      Check whether the @tsk process has the @cap capability in the indicated
  *      credentials.
- *      @tsk contains the task_struct for the process.
  *      @cred contains the credentials to use.
  *      @ns contains the user namespace we want the capability in
  *      @cap contains the capability <include/linux/capability.h>.
@@ -1385,8 +1384,8 @@ struct security_operations {
                        const kernel_cap_t *effective,
                        const kernel_cap_t *inheritable,
                        const kernel_cap_t *permitted);
-        int (*capable) (struct task_struct *tsk, const struct cred *cred,
-                        struct user_namespace *ns, int cap, int audit);
+        int (*capable) (const struct cred *cred, struct user_namespace *ns,
+                        int cap, int audit);
         int (*quotactl) (int cmds, int type, int id, struct super_block *sb);
         int (*quota_on) (struct dentry *dentry);
         int (*syslog) (int type);
@@ -1867,7 +1866,7 @@ static inline int security_capset(struct cred *new,
 static inline int security_capable(struct user_namespace *ns,
                                    const struct cred *cred, int cap)
 {
-        return cap_capable(current, cred, ns, cap, SECURITY_CAP_AUDIT);
+        return cap_capable(cred, ns, cap, SECURITY_CAP_AUDIT);
 }
 
 static inline int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, int cap)
@@ -1875,7 +1874,7 @@ static inline int security_real_capable(struct task_struct *tsk, struct user_nam
         int ret;
 
         rcu_read_lock();
-        ret = cap_capable(tsk, __task_cred(tsk), ns, cap, SECURITY_CAP_AUDIT);
+        ret = cap_capable(__task_cred(tsk), ns, cap, SECURITY_CAP_AUDIT);
         rcu_read_unlock();
         return ret;
 }
@@ -1886,8 +1885,7 @@ int security_real_capable_noaudit(struct task_struct *tsk, struct user_namespace
         int ret;
 
         rcu_read_lock();
-        ret = cap_capable(tsk, __task_cred(tsk), ns, cap,
-                               SECURITY_CAP_NOAUDIT);
+        ret = cap_capable(__task_cred(tsk), ns, cap, SECURITY_CAP_NOAUDIT);
         rcu_read_unlock();
         return ret;
 }