From a4d11eff169073d333d8bc9f6c060fa4dd630bdf 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 (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 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 Signed-off-by: Mark Salyzyn Bug: 24551430 Change-Id: I36a8cc2281dfd68e9a399695f1d7e7b038e105d0 --- ipc/sem.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 09a2fc98..7d91f60a 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -436,13 +436,6 @@ 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++) { @@ -457,6 +450,14 @@ 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();