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>

3 files changed, 14 insertions, 8 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 36f42573a335..07a96474077d 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1115,6 +1115,7 @@ asmlinkage long sys_migrate_pages(pid_t pid, unsigned long maxnode,
         nodemask_t old;
         nodemask_t new;
         nodemask_t task_nodes;
+        uid_t uid, euid;
         int err;
 
         err = get_nodes(&old, old_nodes, maxnode);
@@ -1144,8 +1145,10 @@ asmlinkage long sys_migrate_pages(pid_t pid, unsigned long maxnode,
          * 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;
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;
diff --git a/mm/shmem.c b/mm/shmem.c
index 0ed075215e5f..f1b0d4871f3a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1513,8 +1513,8 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
         inode = new_inode(sb);
         if (inode) {
                 inode->i_mode = mode;
-                inode->i_uid = current->fsuid;
-                inode->i_gid = current->fsgid;
+                inode->i_uid = current_fsuid();
+                inode->i_gid = current_fsgid();
                 inode->i_blocks = 0;
                 inode->i_mapping->backing_dev_info = &shmem_backing_dev_info;
                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
@@ -2278,8 +2278,8 @@ static int shmem_fill_super(struct super_block *sb,
         sbinfo->max_blocks = 0;
         sbinfo->max_inodes = 0;
         sbinfo->mode = S_IRWXUGO | S_ISVTX;
-        sbinfo->uid = current->fsuid;
-        sbinfo->gid = current->fsgid;
+        sbinfo->uid = current_fsuid();
+        sbinfo->gid = current_fsgid();
         sbinfo->mpol = NULL;
         sb->s_fs_info = sbinfo;