Re: [REGRESSION][SECURITY] bpf, s390: verifier/JIT mismatch allows unprivileged kernel memory access

Re: [REGRESSION][SECURITY] bpf, s390: verifier/JIT mismatch allows unprivileged kernel memory access

[Greg KH]

On Thu, Jul 23, 2026 at 04:55:12PM +0900, Min-gyu Kim wrote:
> I have not yet tested a patch.

As you have a reproducer, please create a proposed patch that solves the
issue for you for us to work off of, as our security documentation asks
for.

Also, as you cc:ed public mailing lists, there's no need to get
security@kernel.org involved here.

thanks,

greg k-h

Re: [REGRESSION][SECURITY] bpf, s390: verifier/JIT mismatch allows unprivileged kernel memory access

[Min-gyu Kim]

Hi Greg, Eduard,

Thank you.

Eduard has reproduced the issue and is already working on a fix that extends
compute_live_registers() to track upper 32-bit subregister liveness and removes
the dependency on reg->subreg_def.

Once the patch is posted, I can test it against my reproducer in
the s390x QEMU environment, run the relevant BPF selftests, and report the
results. I can also help prepare or test the regression test if that would be
useful.

I can additionally test older kernels to help determine whether the issue is
triggerable before v6.18, as Eduard suggested.

Best regards,
Min-gyu Kim

2026년 7월 24일 (금) 오후 3:37, Greg KH <greg@kroah.com>님이 작성:
>
> On Thu, Jul 23, 2026 at 04:55:12PM +0900, Min-gyu Kim wrote:
> > I have not yet tested a patch.
>
> As you have a reproducer, please create a proposed patch that solves the
> issue for you for us to work off of, as our security documentation asks
> for.
>
> Also, as you cc:ed public mailing lists, there's no need to get
> security@kernel.org involved here.
>
> thanks,
>
> greg k-h