From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424987AbdEYSvp (ORCPT ); Thu, 25 May 2017 14:51:45 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:34414 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424954AbdEYSvh (ORCPT ); Thu, 25 May 2017 14:51:37 -0400 From: Manfred Spraul To: mtk.manpages@gmail.com, Andrew Morton , Kees Cook Cc: LKML , 1vier1@web.de, Davidlohr Bueso , mingo@kernel.org, peterz@infradead.org, fabf@skynet.be, Manfred Spraul Subject: [PATCH 10/20] ipc/shm: Avoid ipc_rcu_alloc() Date: Thu, 25 May 2017 20:50:57 +0200 Message-Id: <20170525185107.12869-11-manfred@colorfullife.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170525185107.12869-1-manfred@colorfullife.com> References: <20170508222345.GA52073@beast> <20170525185107.12869-1-manfred@colorfullife.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook Instead of using ipc_rcu_alloc() which only performs the refcount bump, open code it. This also allows for shmid_kernel structure layout to be randomized in the future. Signed-off-by: Kees Cook Signed-off-by: Manfred Spraul --- ipc/shm.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 77e1bff..c9f1f30 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -518,6 +518,19 @@ static const struct vm_operations_struct shm_vm_ops = { #endif }; +static struct shmid_kernel *shm_alloc(void) +{ + struct shmid_kernel *shp; + + shp = kvmalloc(sizeof(*shp), GFP_KERNEL); + if (unlikely(!shp)) + return NULL; + + atomic_set(&shp->shm_perm.refcount, 1); + + return shp; +} + /** * newseg - Create a new shared memory segment * @ns: namespace @@ -548,10 +561,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params) ns->shm_tot + numpages > ns->shm_ctlall) return -ENOSPC; - BUILD_BUG_ON(offsetof(struct shmid_kernel, shm_perm) != 0); - - shp = container_of(ipc_rcu_alloc(sizeof(*shp)), struct shmid_kernel, - shm_perm); + shp = shm_alloc(); if (!shp) return -ENOMEM; -- 2.9.3