CRED: Wrap task credential accesses in the SYSV IPC subsystem

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>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index 867e5d6a55c2..0c3debbe32d5 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -752,9 +752,10 @@ asmlinkage long sys_shmctl(int shmid, int cmd, struct shmid_ds __user *buf)
                         goto out_unlock;
 
                 if (!capable(CAP_IPC_LOCK)) {
+                        uid_t euid = current_euid();
                         err = -EPERM;
-                        if (current->euid != shp->shm_perm.uid &&
-                            current->euid != shp->shm_perm.cuid)
+                        if (euid != shp->shm_perm.uid &&
+                            euid != shp->shm_perm.cuid)
                                 goto out_unlock;
                         if (cmd == SHM_LOCK &&
                             !current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)