ipc/sem.c: fully initialize sem_array before making it visible
ipc_addid() makes a new ipc identifier visible to everyone. New objects
start as locked, so that the caller can complete the initialization
after the call. Within struct sem_array, at least sma->sem_base and
sma->sem_nsems are accessed without any locks, therefore this approach
doesn't work.
Thus: Move the ipc_addid() to the end of the initialization.
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Reported-by: Rik van Riel <riel@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/sem.c b/ipc/sem.c
index 454f6c6..53c3310 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -507,13 +507,6 @@
return retval;
}
- id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
- if (id < 0) {
- ipc_rcu_putref(sma, sem_rcu_free);
- return id;
- }
- ns->used_sems += nsems;
-
sma->sem_base = (struct sem *) &sma[1];
for (i = 0; i < nsems; i++) {
@@ -528,6 +521,14 @@
INIT_LIST_HEAD(&sma->list_id);
sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds();
+
+ id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
+ if (id < 0) {
+ ipc_rcu_putref(sma, sem_rcu_free);
+ return id;
+ }
+ ns->used_sems += nsems;
+
sem_unlock(sma, -1);
rcu_read_unlock();