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, 5 insertions, 2 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 6602941bfab0..6263c24c4afe 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1048,6 +1048,7 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
         struct task_struct *task;
         struct mm_struct *mm;
         int err;
+        uid_t uid, euid;
 
         /* Check flags */
         if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL))
@@ -1075,8 +1076,10 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
          * capabilities, superuser privileges or the same
          * userid as the target process.
          */
-        if ((current->euid != task->suid) && (current->euid != task->uid) &&
-            (current->uid != task->suid) && (current->uid != task->uid) &&
+        uid = current_uid();
+        euid = current_euid();
+        if (euid != task->suid && euid != task->uid &&
+            uid  != task->suid && uid  != task->uid &&
             !capable(CAP_SYS_NICE)) {
                 err = -EPERM;
                 goto out;