| Message ID | 1434615176-96706-1-git-send-email-wangnan0@huawei.com |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index a251cf6..6dbdeba 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1020,7 +1020,8 @@ static int check_alu_op(struct reg_state *regs, struct bpf_insn *insn) } /* pattern match 'bpf_add Rx, imm' instruction */ - if (opcode == BPF_ADD && BPF_CLASS(insn->code) == BPF_ALU64 && + if (opcode == BPF_ADD && opcode == BPF_SUB && + BPF_CLASS(insn->code) == BPF_ALU64 && regs[insn->dst_reg].type == FRAME_PTR && BPF_SRC(insn->code) == BPF_K) stack_relative = true;
Original code has a problem, cause following code failed to pass verifier: r1 <- r10 r1 -= 8 r2 = 8 r3 = unsafe pointer call BPF_FUNC_probe_read <-- R1 type=inv expected=fp However, by replacing 'r1 -= 8' to 'r1 += -8' the above program can be loaded successfully. This is because the verifier allows only BPF_ADD instruction on a FRAME_PTR reigster to forge PTR_TO_STACK register, but makes BPF_SUB on FRAME_PTR reigster to get a UNKNOWN_VALUE register. This patch fix it by adding BPF_SUB in stack_relative checking. Signed-off-by: Wang Nan <wangnan0@huawei.com> --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)