| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 090/104] ipc/sem.c: fully initialize sem_array before making it visible | Date | Mon, 26 Oct 2015 13:43:12 +0000 |
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3.16.7-ckt19 -stable review patch. If anyone has any objections, please let me know.
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From: Manfred Spraul <manfred@colorfullife.com>
commit e8577d1f0329d4842e8302e289fb2c22156abef4 upstream.
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: Luis Henriques <luis.henriques@canonical.com> --- ipc/sem.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c index 0e6504c9e907..541cb0ff9bd6 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -524,13 +524,6 @@ 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++) { @@ -545,6 +538,14 @@ 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();
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