From e8577d1f0329d4842e8302e289fb2c22156abef4 Mon Sep 17 00:00:00 2001 From: Manfred Spraul Date: Tue, 2 Dec 2014 15:59:34 -0800 Subject: [PATCH] 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 Reported-by: Rik van Riel Acked-by: Rik van Riel Acked-by: Davidlohr Bueso Acked-by: Rafael Aquini Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 454f6c6020a8..53c3310f41c6 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -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(); -- 2.30.2