From: Kumar Kartikeya Dwivedi memxor@gmail.com
[ Upstream commit 4729445b47efebf089da4ccbcd1b116ffa2ad4af ]
When fed an empty BPF object, bpftool gen skeleton -L crashes at btf__set_fd() since it assumes presence of obj->btf, however for the sequence below clang adds no .BTF section (hence no BTF).
Reproducer:
$ touch a.bpf.c $ clang -O2 -g -target bpf -c a.bpf.c $ bpftool gen skeleton -L a.bpf.o /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ /* THIS FILE IS AUTOGENERATED! */
struct a_bpf { struct bpf_loader_ctx ctx; Segmentation fault (core dumped)
The same occurs for files compiled without BTF info, i.e. without clang's -g flag.
Fixes: 67234743736a (libbpf: Generate loader program out of BPF ELF file.) Signed-off-by: Kumar Kartikeya Dwivedi memxor@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20210930061634.1840768-1-memxor@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index d27e017ebfbe..f1bc09e606cd 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -8115,7 +8115,8 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
if (obj->gen_loader) { /* reset FDs */ - btf__set_fd(obj->btf, -1); + if (obj->btf) + btf__set_fd(obj->btf, -1); for (i = 0; i < obj->nr_maps; i++) obj->maps[i].fd = -1; if (!err)