Re: test_kmod.sh fails with constant blinding

[Yauheni Kaliuta <ykaliuta@redhat.com>]

Hi, Daniel!

>>>>> On Thu, 30 Jun 2022 22:57:37 +0200, Daniel Borkmann  wrote:

 > On 6/30/22 3:19 PM, Yauheni Kaliuta wrote:
 >> Hi!
 >> test_kmod.sh fails for hardened 2 check with
 >> test_bpf: #964 Staggered jumps: JMP_JA FAIL to select_runtime
 >> err=-524
 >> (-ERANGE during constant blinding)
 >> Did I miss something?

 > That could be expected if one of bpf_adj_delta_to_imm() / bpf_adj_delta_to_off()
 > fails given the targets go out of range.

I believe that, but how to fix the test? It should not fail.

 > How do the generated insn look?

The instruction when it fails is

(gdb) p/x insn[0]
$8 = {code = 0xb7, dst_reg = 0x0, src_reg = 0x0, off = 0x0, imm = 0x2aaa}

And it's rewritten as

(gdb) p rewritten 
$9 = 3
(gdb) p/x insn_buff[0]
$10 = {code = 0xb7, dst_reg = 0xb, src_reg = 0x0, off = 0x0, imm = 0x68ad0283}
(gdb) p/x insn_buff[1]
$11 = {code = 0xa7, dst_reg = 0xb, src_reg = 0x0, off = 0x0, imm = 0x68ad2829}
(gdb) p/x insn_buff[2]
$12 = {code = 0xbf, dst_reg = 0x0, src_reg = 0xb, off = 0x0, imm = 0x0}

IIUC.





-- 
WBR,
Yauheni Kaliuta