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>

3 files changed, 19 insertions, 10 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 68eb857cfdea..abda5991d7e3 100644
--- a/ipc/mqueue.c
+++ b/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);
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)
diff --git a/ipc/util.c b/ipc/util.c
index 49b3ea615dc5..c8a76701b6c9 100644
--- a/ipc/util.c
+++ b/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;