From 878b8286d0676876ee9bd1197d9f989805851c91 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Wed, 24 Aug 2022 11:23:39 +0800 Subject: [PATCH] libbpf: Fix segfault in light skeleton for objects without BTF 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/?id=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 Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210930061634.1840768-1-memxor@gmail.com (cherry picked from commit 4729445b47efebf089da4ccbcd1b116ffa2ad4af) Signed-off-by: Wang Yufen --- 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) -- GitLab