| Message ID | 20200820061411.1755905-1-andriin@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next,1/4] libbpf: fix detection of BPF helper call instruction | expand |
On 8/19/20 11:14 PM, Andrii Nakryiko wrote: > 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. > > Reported-by: Yonghong Song <yhs@fb.com> > Fixes: 109cea5a594f ("libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str]") > Signed-off-by: Andrii Nakryiko <andriin@fb.com> Acked-by: Yonghong Song <yhs@fb.com>
On 8/20/20 8:14 AM, Andrii Nakryiko wrote: > 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. > > Reported-by: Yonghong Song <yhs@fb.com> > Fixes: 109cea5a594f ("libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str]") > Signed-off-by: Andrii Nakryiko <andriin@fb.com> Series applied, thanks!
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 77d420c02094..92ca4eb6ba2d 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5844,14 +5844,12 @@ 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;
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. Reported-by: Yonghong Song <yhs@fb.com> Fixes: 109cea5a594f ("libbpf: Sanitize BPF program code for bpf_probe_read_{kernel, user}[_str]") Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/lib/bpf/libbpf.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)