From 88b9e456b1649722673ffa147914299799dc9041 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Fri, 8 Mar 2013 12:43:27 -0800
Subject: ipc: don't allocate a copy larger than max

When MSG_COPY is set, a duplicate message must be allocated for the copy
before locking the queue.  However, the copy could not be larger than was
sent which is limited to msg_ctlmax.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Acked-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/ipc/msg.c b/ipc/msg.c
index 950572f..31cd1bf 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -820,15 +820,17 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
 	struct msg_msg *copy = NULL;
 	unsigned long copy_number = 0;
 
+	ns = current->nsproxy->ipc_ns;
+
 	if (msqid < 0 || (long) bufsz < 0)
 		return -EINVAL;
 	if (msgflg & MSG_COPY) {
-		copy = prepare_copy(buf, bufsz, msgflg, &msgtyp, &copy_number);
+		copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax),
+				    msgflg, &msgtyp, &copy_number);
 		if (IS_ERR(copy))
 			return PTR_ERR(copy);
 	}
 	mode = convert_mode(&msgtyp, msgflg);
-	ns = current->nsproxy->ipc_ns;
 
 	msq = msg_lock_check(ns, msqid);
 	if (IS_ERR(msq)) {
-- 
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