From: Andrii Nakryiko <andrii@kernel.org>
Date: Tue, 14 Dec 2021 15:20:54 -0800
Subject: libbpf: Avoid reading past ELF data section end when copying license
Patch-mainline: v5.17-rc1
Git-commit: f97982398cc1c92f2e9bd0ef1ef870a5a729b0ac
References: jsc#PED-1368

Fix possible read beyond ELF "license" data section if the license
string is not properly zero-terminated. Use the fact that libbpf_strlcpy
never accesses the (N-1)st byte of the source string because it's
replaced with '\0' anyways.

If this happens, it's a violation of contract between libbpf and a user,
but not handling this more robustly upsets CIFuzz, so given the fix is
trivial, let's fix the potential issue.

Fixes: 9fc205b413b3 ("libbpf: Add sane strncpy alternative and use it internally")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211214232054.3458774-1-andrii@kernel.org
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/lib/bpf/libbpf.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1320,7 +1320,10 @@ static int bpf_object__check_endianness(
 static int
 bpf_object__init_license(struct bpf_object *obj, void *data, size_t size)
 {
-	libbpf_strlcpy(obj->license, data, sizeof(obj->license));
+	/* libbpf_strlcpy() only copies first N - 1 bytes, so size + 1 won't
+	 * go over allowed ELF data section buffer
+	 */
+	libbpf_strlcpy(obj->license, data, min(size + 1, sizeof(obj->license)));
 	pr_debug("license of %s is %s\n", obj->path, obj->license);
 	return 0;
 }