From 52f908904e7e05b6300162faa48152df073be645 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 12 Jul 2017 14:35:07 -0700 Subject: [PATCH] ipc/msg: avoid ipc_rcu_alloc() Instead of using ipc_rcu_alloc() which only performs the refcount bump, open code it. This also allows for msg_queue structure layout to be randomized in the future. Link: http://lkml.kernel.org/r/20170525185107.12869-12-manfred@colorfullife.com Signed-off-by: Kees Cook Signed-off-by: Manfred Spraul Cc: Davidlohr Bueso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/msg.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/ipc/msg.c b/ipc/msg.c index 25d43e27ef12..10094a731b8e 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -109,6 +109,19 @@ static void msg_rcu_free(struct rcu_head *head) __msg_free(msq); } +static struct msg_queue *msg_alloc(void) +{ + struct msg_queue *msq; + + msq = kvmalloc(sizeof(*msq), GFP_KERNEL); + if (unlikely(!msq)) + return NULL; + + atomic_set(&msq->q_perm.refcount, 1); + + return msq; +} + /** * newque - Create a new msg queue * @ns: namespace @@ -123,10 +136,7 @@ static int newque(struct ipc_namespace *ns, struct ipc_params *params) key_t key = params->key; int msgflg = params->flg; - BUILD_BUG_ON(offsetof(struct msg_queue, q_perm) != 0); - - msq = container_of(ipc_rcu_alloc(sizeof(*msq)), struct msg_queue, - q_perm); + msq = msg_alloc(); if (!msq) return -ENOMEM;