--- /dev/null
+From 4617f564c06117c7d1b611be49521a4430042287 Mon Sep 17 00:00:00 2001
+From: Adrian Salido <salidoa@google.com>
+Date: Thu, 27 Apr 2017 10:32:55 -0700
+Subject: dm ioctl: prevent stack leak in dm ioctl call
+
+From: Adrian Salido <salidoa@google.com>
+
+commit 4617f564c06117c7d1b611be49521a4430042287 upstream.
+
+When calling a dm ioctl that doesn't process any data
+(IOCTL_FLAGS_NO_PARAMS), the contents of the data field in struct
+dm_ioctl are left initialized. Current code is incorrectly extending
+the size of data copied back to user, causing the contents of kernel
+stack to be leaked to user. Fix by only copying contents before data
+and allow the functions processing the ioctl to override.
+
+Signed-off-by: Adrian Salido <salidoa@google.com>
+Reviewed-by: Alasdair G Kergon <agk@redhat.com>
+Signed-off-by: Mike Snitzer <snitzer@redhat.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/md/dm-ioctl.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/drivers/md/dm-ioctl.c
++++ b/drivers/md/dm-ioctl.c
+@@ -1848,7 +1848,7 @@ static int ctl_ioctl(uint command, struc
+ if (r)
+ goto out;
+
+- param->data_size = sizeof(*param);
++ param->data_size = offsetof(struct dm_ioctl, data);
+ r = fn(param, input_param_size);
+
+ if (unlikely(param->flags & DM_BUFFER_FULL_FLAG) &&