IPC: consolidate all xxxctl_down() functions

semctl_down(), msgctl_down() and shmctl_down() are used to handle the same set
of commands for each kind of IPC.  They all start to do the same job (they
retrieve the ipc and do some permission checks) before handling the commands
on their own.

This patch proposes to consolidate this by moving these same pieces of code
into one common function called ipcctl_pre_down().

It simplifies a little these xxxctl_down() functions and increases a little
the maintainability.

Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 43 deletions

diff --git a/ipc/msg.c b/ipc/msg.c
index 87d8b3852300..4a858f98a760 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -142,21 +142,6 @@ void __init msg_init(void)
 }
 
 /*
- * This routine is called in the paths where the rw_mutex is held to protect
- * access to the idr tree.
- */
-static inline struct msg_queue *msg_lock_check_down(struct ipc_namespace *ns,
-                                                int id)
-{
-        struct kern_ipc_perm *ipcp = ipc_lock_check_down(&msg_ids(ns), id);
-
-        if (IS_ERR(ipcp))
-                return (struct msg_queue *)ipcp;
-
-        return container_of(ipcp, struct msg_queue, q_perm);
-}
-
-/*
  * msg_lock_(check_) routines are called in the paths where the rw_mutex
  * is not held.
  */
@@ -437,35 +422,12 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
                         return -EFAULT;
         }
 
-        down_write(&msg_ids(ns).rw_mutex);
-        msq = msg_lock_check_down(ns, msqid);
-        if (IS_ERR(msq)) {
-                err = PTR_ERR(msq);
-                goto out_up;
-        }
-
-        ipcp = &msq->q_perm;
-
-        err = audit_ipc_obj(ipcp);
-        if (err)
-                goto out_unlock;
-
-        if (cmd == IPC_SET) {
-                err = audit_ipc_set_perm(msqid64.msg_qbytes,
-                                         msqid64.msg_perm.uid,
-                                         msqid64.msg_perm.gid,
-                                         msqid64.msg_perm.mode);
-                if (err)
-                        goto out_unlock;
-        }
+        ipcp = ipcctl_pre_down(&msg_ids(ns), msqid, cmd,
+                               &msqid64.msg_perm, msqid64.msg_qbytes);
+        if (IS_ERR(ipcp))
+                return PTR_ERR(ipcp);
 
-        if (current->euid != ipcp->cuid &&
-            current->euid != ipcp->uid &&
-            !capable(CAP_SYS_ADMIN)) {
-                /* We _could_ check for CAP_CHOWN above, but we don't */
-                err = -EPERM;
-                goto out_unlock;
-        }
+        msq = container_of(ipcp, struct msg_queue, q_perm);
 
         err = security_msg_queue_msgctl(msq, cmd);
         if (err)