From d10c84c4bc78e8ebd8c6ebf70126ad3cb0ba1c46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pierre-Cl=C3=A9ment=20Tosi?= <ptosi@google.com>
Date: Tue, 13 Sep 2022 16:58:15 +0100
Subject: [PATCH] libfdt: fdt_path_offset_namelen: Reject empty paths

Make empty paths result in FDT_ERR_BADPATH.

Per the specification (v0.4-rc4):

> The convention for specifying a device path is:
>     /node-name-1/node-name-2/node-name-N
>
> The path to the root node is /.
>
> A unit address may be omitted if the full path to the
> node is unambiguous.

Bug: 246465319
Test: libfdt_fuzzer  # clusterfuzz/testcase-detail/4530863420604416
Change-Id: I14ab0a074ab994c1f598243d2d5795d2cd9a853a
(cherry picked from commit 3c28f3e3a1724c288d19f1b1a139cf57bfe1af33)
---
 libfdt/fdt_ro.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 08de2cc..3b65f16 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -188,6 +188,9 @@ int fdt_path_offset_namelen(const void *fdt, const char *path, int namelen)
 
 	FDT_CHECK_HEADER(fdt);
 
+	if (namelen < 1)
+		return -FDT_ERR_BADPATH;
+
 	/* see if we have an alias */
 	if (*path != '/') {
 		const char *q = memchr(path, '/', end - p);