Commit 9b2f6fec authored Aug 19, 2020 by Andrii Nakryiko Committed by Daniel Borkmann Aug 20, 2020

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: 109cea5a ("libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str]")
Reported-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200820061411.1755905-1-andriin@fb.com

parent 0bc23a1d

tools/lib/bpf/libbpf.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -5840,13 +5840,11 @@ 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)
		insn->src_reg == 0 &&
		insn->dst_reg == 0) {
		*func_id = insn->imm;
		return true;
		}

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