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

(cherry pick from commit e8577d1f0329d4842e8302e289fb2c22156abef4)

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>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 24551430
Change-Id: I36a8cc2281dfd68e9a399695f1d7e7b038e105d0
This commit is contained in:
Manfred Spraul 2014-12-02 15:59:34 -08:00 committed by Srinivasarao P
parent 234adae187
commit 7eb371bed3
1 changed files with 8 additions and 7 deletions
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15
ipc/sem.c
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@ -508,13 +508,6 @@ 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++) {
@ -529,6 +522,14 @@ 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();