From: Andrii Nakryiko andriin@fb.com
[ Upstream commit 5d01ab7bac467edfc530e6ccf953921def935c62 ]
Libbpf stores associated BTF FD per each instance of bpf_program. When program is unloaded, that FD is closed. This is wrong, because leads to a race and possibly closing of unrelated files, if application simultaneously opens new files while bpf_programs are unloaded.
It's also unnecessary, because struct btf "owns" that FD, and btf__free(), called from bpf_object__close() will close it. Thus the fix is to never have per-program BTF FD and fetch it from obj->btf, when necessary.
Fixes: 2993e0515bb4 ("tools/bpf: add support to read .BTF.ext sections") Reported-by: Andrey Ignatov rdna@fb.com Signed-off-by: Andrii Nakryiko andriin@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3865a5d272514..e308fcf16cdd0 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -178,7 +178,6 @@ struct bpf_program { bpf_program_clear_priv_t clear_priv;
enum bpf_attach_type expected_attach_type; - int btf_fd; void *func_info; __u32 func_info_rec_size; __u32 func_info_cnt; @@ -305,7 +304,6 @@ void bpf_program__unload(struct bpf_program *prog) prog->instances.nr = -1; zfree(&prog->instances.fds);
- zclose(prog->btf_fd); zfree(&prog->func_info); zfree(&prog->line_info); } @@ -382,7 +380,6 @@ bpf_program__init(void *data, size_t size, char *section_name, int idx, prog->instances.fds = NULL; prog->instances.nr = -1; prog->type = BPF_PROG_TYPE_UNSPEC; - prog->btf_fd = -1;
return 0; errout: @@ -1883,9 +1880,6 @@ bpf_program_reloc_btf_ext(struct bpf_program *prog, struct bpf_object *obj, prog->line_info_rec_size = btf_ext__line_info_rec_size(obj->btf_ext); }
- if (!insn_offset) - prog->btf_fd = btf__fd(obj->btf); - return 0; }
@@ -2060,7 +2054,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, char *cp, errmsg[STRERR_BUFSIZE]; int log_buf_size = BPF_LOG_BUF_SIZE; char *log_buf; - int ret; + int btf_fd, ret;
memset(&load_attr, 0, sizeof(struct bpf_load_program_attr)); load_attr.prog_type = prog->type; @@ -2072,7 +2066,8 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, load_attr.license = license; load_attr.kern_version = kern_version; load_attr.prog_ifindex = prog->prog_ifindex; - load_attr.prog_btf_fd = prog->btf_fd >= 0 ? prog->btf_fd : 0; + btf_fd = bpf_object__btf_fd(prog->obj); + load_attr.prog_btf_fd = btf_fd >= 0 ? btf_fd : 0; 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;