From 489ed1cb3c63477bc0e12e6ac20577009894c875 Mon Sep 17 00:00:00 2001
From: Manfred Spraul <manfred@colorfullife.com>
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 <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
---
ipc/sem.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index db9d241af133..082d2f674f1d 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -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();
--
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