Re: [syzbot] [bpf?] KMSAN: uninit-value in ieee802154_subif_start_xmit

On Mon, 2023-08-07 at 16:11 +0300, Eduard Zingerman wrote:
[...]

  $ bpftool prog dump jited id <some-id>
  bpf_prog_ebeed182d92b487f:
     0: nopl    (%rax,%rax)
     5: nop
     7: pushq   %rbp
     8: movq    %rsp, %rbp
     b: subq    $8, %rsp
    12: movl    $553656332, -8(%rbp)
    19: movswq  %bp, %rdi            ; <---- Note movswq %bp !
    1d: addq    $-8, %rdi
    21: movl    $3, %esi
    26: cmpq    %rdi, %rsi
    29: jbe 0x2b
    2b: callq   0xffffffffe11c484c
    30: xorl    %eax, %eax
    32: leave
    33: retq

Note jit instruction #19 corresponding to BPF instruction #1, which
loads truncated and sign-extended value of %rbp's first byte as an
address of format string.

Correction: sign-extended value of %rbp's first *two* bytes,
disassembly with opcodes:

  19:	movswq	%bp, %rdi
    48 0f bf fd 

[...]