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>

ipc/mqueue.c

@@ -117,8 +117,8 @@ static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
 	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_mtime = inode->i_ctime = inode->i_atime =
 				CURRENT_TIME;
@@ -507,7 +507,7 @@ static void __do_notify(struct mqueue_inode_info *info)
 			sig_i.si_code = SI_MESGQ;
 			sig_i.si_value = info->notify.sigev_value;
 			sig_i.si_pid = task_tgid_vnr(current);
-			sig_i.si_uid = current->uid;
+			sig_i.si_uid = current_uid();
 
 			kill_pid_info(info->notify.sigev_signo,
 				      &sig_i, info->notify_owner);

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)

ipc/util.c

@@ -258,6 +258,8 @@ int ipc_get_maxid(struct ipc_ids *ids)
  
 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
+	uid_t euid;
+	gid_t egid;
 	int id, err;
 
 	if (size > IPCMNI)
@@ -272,8 +274,9 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 
 	ids->in_use++;
 
-	new->cuid = new->uid = current->euid;
-	new->gid = new->cgid = current->egid;
+	current_euid_egid(&euid, &egid);
+	new->cuid = new->uid = euid;
+	new->gid = new->cgid = egid;
 
 	new->seq = ids->seq++;
 	if(ids->seq > ids->seq_max)
@@ -616,13 +619,15 @@ void ipc_rcu_putref(void *ptr)
  
 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
 {	/* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
+	uid_t euid = current_euid();
 	int requested_mode, granted_mode, err;
 
 	if (unlikely((err = audit_ipc_obj(ipcp))))
 		return err;
 	requested_mode = (flag >> 6) | (flag >> 3) | flag;
 	granted_mode = ipcp->mode;
-	if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
+	if (euid == ipcp->cuid ||
+	    euid == ipcp->uid)
 		granted_mode >>= 6;
 	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 		granted_mode >>= 3;
@@ -784,6 +789,7 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_ids *ids, int id, int cmd,
 				      struct ipc64_perm *perm, int extra_perm)
 {
 	struct kern_ipc_perm *ipcp;
+	uid_t euid;
 	int err;
 
 	down_write(&ids->rw_mutex);
@@ -803,8 +809,10 @@ struct kern_ipc_perm *ipcctl_pre_down(struct ipc_ids *ids, int id, int cmd,
 		if (err)
 			goto out_unlock;
 	}
-	if (current->euid == ipcp->cuid ||
-	    current->euid == ipcp->uid || capable(CAP_SYS_ADMIN))
+
+	euid = current_euid();
+	if (euid == ipcp->cuid ||
+	    euid == ipcp->uid  || capable(CAP_SYS_ADMIN))
 		return ipcp;
 
 	err = -EPERM;