ipc: initialize structure memory to zero for compat functions

This takes care of leaking uninitialized kernel stack memory to
userspace from non-zeroed fields in structs in compat ipc functions.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Manfred Spraul <manfred@colorfullife.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/ipc/compat_mq.c b/ipc/compat_mq.c
index d8d1e9f..380ea4f 100644
--- a/ipc/compat_mq.c
+++ b/ipc/compat_mq.c
@@ -53,6 +53,9 @@
 	void __user *p = NULL;
 	if (u_attr && oflag & O_CREAT) {
 		struct mq_attr attr;
+
+		memset(&attr, 0, sizeof(attr));
+
 		p = compat_alloc_user_space(sizeof(attr));
 		if (get_compat_mq_attr(&attr, u_attr) ||
 		    copy_to_user(p, &attr, sizeof(attr)))
@@ -127,6 +130,8 @@
 	struct mq_attr __user *p = compat_alloc_user_space(2 * sizeof(*p));
 	long ret;
 
+	memset(&mqstat, 0, sizeof(mqstat));
+
 	if (u_mqstat) {
 		if (get_compat_mq_attr(&mqstat, u_mqstat) ||
 		    copy_to_user(p, &mqstat, sizeof(mqstat)))