releases/6.9.3/libbpf-prevent-null-pointer-dereference-when-prog-to.patch

From 3638d74cf735ac1800e298b8422e38eb1c988b3e Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Thu, 14 Mar 2024 15:04:38 +0000
Subject: libbpf: Prevent null-pointer dereference when prog to load has no BTF

From: Quentin Monnet <qmo@kernel.org>

[ Upstream commit 9bf48fa19a4b1d186e08b20bf7e5de26a15644fb ]

In bpf_objec_load_prog(), there's no guarantee that obj->btf is non-NULL
when passing it to btf__fd(), and this function does not perform any
check before dereferencing its argument (as bpf_object__btf_fd() used to
do). As a consequence, we get segmentation fault errors in bpftool (for
example) when trying to load programs that come without BTF information.

v2: Keep btf__fd() in the fix instead of reverting to bpf_object__btf_fd().

Fixes: df7c3f7d3a3d ("libbpf: make uniform use of btf__fd() accessor inside libbpf")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240314150438.232462-1-qmo@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/lib/bpf/libbpf.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a2061fcd612d7..4980ed4f7559b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7321,9 +7321,9 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
 	char *cp, errmsg[STRERR_BUFSIZE];
 	size_t log_buf_size = 0;
 	char *log_buf = NULL, *tmp;
-	int btf_fd, ret, err;
 	bool own_log_buf = true;
 	__u32 log_level = prog->log_level;
+	int ret, err;
 
 	if (prog->type == BPF_PROG_TYPE_UNSPEC) {
 		/*
@@ -7347,9 +7347,8 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
 	load_attr.prog_ifindex = prog->prog_ifindex;
 
 	/* specify func_info/line_info only if kernel supports them */
-	btf_fd = btf__fd(obj->btf);
-	if (btf_fd >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
-		load_attr.prog_btf_fd = btf_fd;
+	if (obj->btf && btf__fd(obj->btf) >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
+		load_attr.prog_btf_fd = btf__fd(obj->btf);
 		load_attr.func_info = prog->func_info;
 		load_attr.func_info_rec_size = prog->func_info_rec_size;
 		load_attr.func_info_cnt = prog->func_info_cnt;
-- 
2.43.0