From: Kumar Kartikeya Dwivedi memxor@gmail.com
mainline inclusion from mainline-5.15-rc5 commit 4729445b47efebf089da4ccbcd1b116ffa2ad4af category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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 (cherry picked from commit 4729445b47efebf089da4ccbcd1b116ffa2ad4af) Signed-off-by: Wang Yufen wangyufen@huawei.com --- 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 1781d0edcdf0..fa45f5643c9b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -6860,7 +6860,8 @@ 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)