CRED: Wrap task credential accesses in the core kernel

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-audit@redhat.com
Cc: containers@lists.linux-foundation.org
Cc: linux-mm@kvack.org
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 7 insertions, 4 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index e8819bc6f462..c3b8b1fcde0d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5128,6 +5128,7 @@ static int __sched_setscheduler(struct task_struct *p, int policy,
         unsigned long flags;
         const struct sched_class *prev_class = p->sched_class;
         struct rq *rq;
+        uid_t euid;
 
         /* may grab non-irq protected spin_locks */
         BUG_ON(in_interrupt());
@@ -5180,8 +5181,9 @@ recheck:
                         return -EPERM;
 
                 /* can't change other user's priorities */
-                if ((current->euid != p->euid) &&
-                    (current->euid != p->uid))
+                euid = current_euid();
+                if (euid != p->euid &&
+                    euid != p->uid)
                         return -EPERM;
         }
 
@@ -5392,6 +5394,7 @@ long sched_setaffinity(pid_t pid, const cpumask_t *in_mask)
         cpumask_t cpus_allowed;
         cpumask_t new_mask = *in_mask;
         struct task_struct *p;
+        uid_t euid;
         int retval;
 
         get_online_cpus();
@@ -5412,9 +5415,9 @@ long sched_setaffinity(pid_t pid, const cpumask_t *in_mask)
         get_task_struct(p);
         read_unlock(&tasklist_lock);
 
+        euid = current_euid();
         retval = -EPERM;
-        if ((current->euid != p->euid) && (current->euid != p->uid) &&
-                        !capable(CAP_SYS_NICE))
+        if (euid != p->euid && euid != p->uid && !capable(CAP_SYS_NICE))
                 goto out_unlock;
 
         retval = security_task_setscheduler(p, 0, NULL);