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ipc/sem.c: fully initialize sem_array before making it visible

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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 <[email protected]>
Reported-by: Rik van Riel <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Acked-by: Davidlohr Bueso <[email protected]>
Acked-by: Rafael Aquini <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Manfred Spraul authored and Linus Torvalds committed 2014-12-03 09:36:03 -08:00
1 parent 92788ac1eb
commit e8577d1f03
1 file changed
+8 -7
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ipc/sem.c
+8 -7
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@@ -507,13 +507,6 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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();