From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761473Ab3JPRtA (ORCPT ); Wed, 16 Oct 2013 13:49:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36039 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933715Ab3JPRqm (ORCPT ); Wed, 16 Oct 2013 13:46:42 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Manfred Spraul , Davidlohr Bueso , Mike Galbraith , Rik van Riel , Andrew Morton , Linus Torvalds Subject: [ 48/50] ipc/sem.c: synchronize the proc interface Date: Wed, 16 Oct 2013 10:45:34 -0700 Message-Id: <20131016174404.249606640@linuxfoundation.org> X-Mailer: git-send-email 1.8.4.3.gca3854a In-Reply-To: <20131016174358.335646140@linuxfoundation.org> References: <20131016174358.335646140@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.11-stable review patch. If anyone has any objections, please let me know. ------------------ From: Manfred Spraul commit d8c633766ad88527f25d9f81a5c2f083d78a2b39 upstream. The proc interface is not aware of sem_lock(), it instead calls ipc_lock_object() directly. This means that simple semop() operations can run in parallel with the proc interface. Right now, this is uncritical, because the implementation doesn't do anything that requires a proper synchronization. But it is dangerous and therefore should be fixed. Signed-off-by: Manfred Spraul Cc: Davidlohr Bueso Cc: Mike Galbraith Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- ipc/sem.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2103,6 +2103,14 @@ static int sysvipc_sem_proc_show(struct struct sem_array *sma = it; time_t sem_otime; + /* + * The proc interface isn't aware of sem_lock(), it calls + * ipc_lock_object() directly (in sysvipc_find_ipc). + * In order to stay compatible with sem_lock(), we must wait until + * all simple semop() calls have left their critical regions. + */ + sem_wait_array(sma); + sem_otime = get_semotime(sma); return seq_printf(s,