Commit 51c23b7b authored Jul 12, 2017 by Manfred Spraul Committed by Linus Torvalds Jul 12, 2017

ipc/msg.c: avoid ipc_rcu_putref for failed ipc_addid()

Loosely based on a patch from Kees Cook <keescook@chromium.org>:
 - id and retval can be merged
 - if ipc_addid() fails, then use call_rcu() directly.

The difference is that call_rcu is used for failed ipc_addid() calls, to
continue to guaranteed an rcu delay for security_msg_queue_free().

Link: http://lkml.kernel.org/r/20170525185107.12869-16-manfred@colorfullife.com


Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a2642f87

ipc/msg.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -132,7 +132,7 @@ static struct msg_queue *msg_alloc(void)
		static int newque(struct ipc_namespace ns, struct ipc_params params)
		{
		struct msg_queue *msq;
		int id, retval;
		int retval;
		key_t key = params->key;
		int msgflg = params->flg;

		@@ -160,10 +160,10 @@ static int newque(struct ipc_namespace ns, struct ipc_params params)
		INIT_LIST_HEAD(&msq->q_senders);

		/* ipc_addid() locks msq upon success. */
		id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
		if (id < 0) {
		ipc_rcu_putref(&msq->q_perm, msg_rcu_free);
		return id;
		retval = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
		if (retval < 0) {
		call_rcu(&msq->q_perm.rcu, msg_rcu_free);
		return retval;
		}

		ipc_unlock_object(&msq->q_perm);

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