patches/0923-of-overlay-Fix-out-of-bounds-write-in-init_overlay_c.patch

From e8b167d256e67d6b1f40ca905887c7e26d55ce67 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas@glider.be>
Date: Fri, 8 Dec 2017 14:13:02 +0100
Subject: [PATCH 0923/1795] of: overlay: Fix out-of-bounds write in
 init_overlay_changeset()

If an overlay has no "__symbols__" node, but it has nodes without
"__overlay__" subnodes at the end (e.g. a "__fixups__" node), after
filling in all fragments for nodes with "__overlay__" subnodes,
"fragment = &fragments[cnt]" will point beyond the end of the allocated
array.

Hence writing to "fragment->overlay" will overwrite unallocated memory,
which may lead to a crash later.

Fix this by deferring both the assignment to "fragment" and the
offending write afterwards until we know for sure the node has an
"__overlay__" subnode, and thus a valid entry in "fragments[]".

Fixes: 61b4de4e0b384f4a ("of: overlay: minor restructuring")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>
(cherry picked from commit 35e691eddca565f475ba69ff84ca0c9db3b3257b)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/of/overlay.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index fcce5cdbe229..83bb2edfc65c 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -572,9 +572,10 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
 
 	cnt = 0;
 	for_each_child_of_node(tree, node) {
-		fragment = &fragments[cnt];
-		fragment->overlay = of_get_child_by_name(node, "__overlay__");
-		if (fragment->overlay) {
+		overlay_node = of_get_child_by_name(node, "__overlay__");
+		if (overlay_node) {
+			fragment = &fragments[cnt];
+			fragment->overlay = overlay_node;
 			fragment->target = find_target_node(node);
 			if (!fragment->target) {
 				of_node_put(fragment->overlay);
-- 
2.19.0