From 9b2f6fecf3b77d2457a13f77a563c07304f15775 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 19 Aug 2020 23:14:08 -0700 Subject: [PATCH] libbpf: Fix detection of BPF helper call instruction BPF_CALL | BPF_JMP32 is explicitly not allowed by verifier for BPF helper calls, so don't detect it as a valid call. Also drop the check on func_id pointer, as it's currently always non-null. Fixes: 109cea5a594f ("libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str]") Reported-by: Yonghong Song Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/bpf/20200820061411.1755905-1-andriin@fb.com --- tools/lib/bpf/libbpf.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 829d62a3ad5f1..0bc1fd813408e 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5840,14 +5840,12 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) static bool insn_is_helper_call(struct bpf_insn *insn, enum bpf_func_id *func_id) { - __u8 class = BPF_CLASS(insn->code); - - if ((class == BPF_JMP || class == BPF_JMP32) && + if (BPF_CLASS(insn->code) == BPF_JMP && BPF_OP(insn->code) == BPF_CALL && BPF_SRC(insn->code) == BPF_K && - insn->src_reg == 0 && insn->dst_reg == 0) { - if (func_id) - *func_id = insn->imm; + insn->src_reg == 0 && + insn->dst_reg == 0) { + *func_id = insn->imm; return true; } return false; -- 2.30.2