[PATCH v6 04/17] lib/bootconfig: fix off-by-one in xbc_verify_tree() next node check

[Josh Law <objecting@objecting.org>]

Valid node indices are 0 to xbc_node_num-1, so a next value equal to
xbc_node_num is out of bounds.  Use >= instead of > to catch this.

A malformed or corrupt bootconfig could pass tree verification with
an out-of-bounds next index.  On subsequent tree traversal at boot
time, xbc_node_get_next() would return a pointer past the allocated
xbc_nodes array, causing an out-of-bounds read of kernel memory.

Signed-off-by: Josh Law <objecting@objecting.org>
---
 lib/bootconfig.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 58d6ae297280..56fbedc9e725 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -816,7 +816,7 @@ static int __init xbc_verify_tree(void)
 	}
 
 	for (i = 0; i < xbc_node_num; i++) {
-		if (xbc_nodes[i].next > xbc_node_num) {
+		if (xbc_nodes[i].next >= xbc_node_num) {
 			return xbc_parse_error("No closing brace",
 				xbc_node_get_data(xbc_nodes + i));
 		}
-- 
2.34.1