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/security/commoncap.c b/security/commoncap.c
index a93b3b733079..89f02ff66af9 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -66,7 +66,6 @@ EXPORT_SYMBOL(cap_netlink_recv);
 
 /**
  * cap_capable - Determine whether a task has a particular effective capability
- * @tsk: The task to query
  * @cred: The credentials to use
  * @ns:  The user namespace in which we need the capability
  * @cap: The capability to check for
@@ -80,8 +79,8 @@ EXPORT_SYMBOL(cap_netlink_recv);
  * cap_has_capability() returns 0 when a task has a capability, but the
  * kernel's capable() and has_capability() returns 1 for this case.
  */
-int cap_capable(struct task_struct *tsk, const struct cred *cred,
-                struct user_namespace *targ_ns, int cap, int audit)
+int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
+                int cap, int audit)
 {
         for (;;) {
                 /* The creator of the user namespace has all caps. */
@@ -222,9 +221,8 @@ static inline int cap_inh_is_capped(void)
         /* they are so limited unless the current task has the CAP_SETPCAP
          * capability
          */
-        if (cap_capable(current, current_cred(),
-                        current_cred()->user->user_ns, CAP_SETPCAP,
-                        SECURITY_CAP_AUDIT) == 0)
+        if (cap_capable(current_cred(), current_cred()->user->user_ns,
+                        CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
                 return 0;
         return 1;
 }
@@ -870,7 +868,7 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
                      & (new->securebits ^ arg2))                        /*[1]*/
                     || ((new->securebits & SECURE_ALL_LOCKS & ~arg2))   /*[2]*/
                     || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))   /*[3]*/
-                    || (cap_capable(current, current_cred(),
+                    || (cap_capable(current_cred(),
                                     current_cred()->user->user_ns, CAP_SETPCAP,
                                     SECURITY_CAP_AUDIT) != 0)           /*[4]*/
                         /*
@@ -936,7 +934,7 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
 {
         int cap_sys_admin = 0;
 
-        if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN,
+        if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
                         SECURITY_CAP_NOAUDIT) == 0)
                 cap_sys_admin = 1;
         return __vm_enough_memory(mm, pages, cap_sys_admin);
@@ -963,7 +961,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot,
         int ret = 0;
 
         if (addr < dac_mmap_min_addr) {
-                ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO,
+                ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
                                   SECURITY_CAP_AUDIT);
                 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
                 if (ret == 0)