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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: 109cea5a59 ("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
This commit is contained in:
Andrii Nakryiko 2020-08-19 23:14:08 -07:00 committed by Daniel Borkmann
parent 0bc23a1d1c
commit 9b2f6fecf3
1 changed files with 4 additions and 6 deletions
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10
tools/lib/bpf/libbpf.c
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@ -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;