From 04efe5911fb30664a56ec63d272a0f39a71545db Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 19 Jul 2019 12:32:42 -0700 Subject: [PATCH] libbpf: fix SIGSEGV when BTF loading fails, but .BTF.ext exists In case when BTF loading fails despite sanitization, but BPF object has .BTF.ext loaded as well, we free and null obj->btf, but not obj->btf_ext. This leads to an attempt to relocate .BTF.ext later on during bpf_object__load(), which assumes obj->btf is present. This leads to SIGSEGV on null pointer access. Fix bug by freeing and nulling obj->btf_ext as well. Signed-off-by: Andrii Nakryiko Signed-off-by: Alexei Starovoitov --- tools/lib/bpf/libbpf.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 794dd5064ae8..87168f21ef43 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1500,6 +1500,12 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj) BTF_ELF_SEC, err); btf__free(obj->btf); obj->btf = NULL; + /* btf_ext can't exist without btf, so free it as well */ + if (obj->btf_ext) { + btf_ext__free(obj->btf_ext); + obj->btf_ext = NULL; + } + if (bpf_object__is_btf_mandatory(obj)) return err; } -- 2.30.2