ipc,msg: make msgctl_nolock lockless

[cascardo/linux.git] / ipc / util.c

diff --git a/ipc/util.c b/ipc/util.c
index 809ec5e..a0c139f 100644 (file)
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -246,9 +246,8 @@ int ipc_get_maxid(struct ipc_ids *ids)
  *     is returned. The 'new' entry is returned in a locked state on success.
  *     On failure the entry is not locked and a negative err-code is returned.
  *
- *     Called with ipc_ids.rw_mutex held as a writer.
+ *     Called with writer ipc_ids.rw_mutex held.
  */
- 
 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 {
        kuid_t euid;
@@ -747,8 +746,10 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
  * It must be called without any lock held and
  *  - retrieves the ipc with the given id in the given table.
  *  - performs some audit and permission check, depending on the given cmd
- *  - returns the ipc with both ipc and rw_mutex locks held in case of success
+ *  - returns the ipc with the ipc lock held in case of success
  *    or an err-code without any lock held otherwise.
+ *
+ * Call holding the both the rw_mutex and the rcu read lock.
  */
 struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
                                      struct ipc_ids *ids, int id, int cmd,
@@ -773,13 +774,10 @@ struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
        int err = -EPERM;
        struct kern_ipc_perm *ipcp;
 
-       down_write(&ids->rw_mutex);
-       rcu_read_lock();
-
        ipcp = ipc_obtain_object_check(ids, id);
        if (IS_ERR(ipcp)) {
                err = PTR_ERR(ipcp);
-               goto out_up;
+               goto err;
        }
 
        audit_ipc_obj(ipcp);
@@ -790,16 +788,8 @@ struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
        euid = current_euid();
        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
-               return ipcp;
-
-out_up:
-       /*
-        * Unsuccessful lookup, unlock and return
-        * the corresponding error.
-        */
-       rcu_read_unlock();
-       up_write(&ids->rw_mutex);
-
+               return ipcp; /* successful lookup */
+err:
        return ERR_PTR(err);
 }