Re: port-amd64/58366: KASLR broken

[Harold Gutch <logix%foobar.franken.de@localhost>]

Hi,

On Tue, Jun 25, 2024 at 06:05:01PM +0000, Taylor R Campbell wrote:
> The following reply was made to PR port-amd64/58366; it has been noted by GNATS.
> 
> From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
> To: Harold Gutch <logix%foobar.franken.de@localhost>
> Cc: gnats-bugs%NetBSD.org@localhost, port-amd64-maintainer%NetBSD.org@localhost,
> 	gnats-admin%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
> Subject: Re: port-amd64/58366: KASLR broken
> Date: Tue, 25 Jun 2024 18:03:39 +0000
> 
>  > Date: Tue, 25 Jun 2024 18:07:44 +0200
>  > From: Harold Gutch <logix%foobar.franken.de@localhost>
>  >=20
>  > On Tue, Jun 25, 2024 at 01:36:07PM +0000, Taylor R Campbell wrote:
>  > > Can you please try the attached patch?
>  >=20
>  > Thanks, that gets past prekern but then panics:
>  >=20
>  > [   1.4884345] trap type 4 code 0 rip 0xffffffffacefd336 cs 0x8 rflags 0x=
>  246 cr2 0 ilevel 0x6 rsp 0xffffffffe9e85a80
>  > [   1.5005255] curlwp 0xffffffffa0be8480 pid 0.0 lowest kstack 0xffffffff=
>  e9e812c0
>  > kernel: protection fault trap, code=3D0
>  > Stopped in pid 0.0 (system) at  netbsd:aes_sse2_selftest+0xb9:  ???
>  > aes_sse2_selftest() at netbsd:aes_sse2_selftest+0xb9
>  
>  Can you try the patch on top of the first revision you found with
>  broken prekern?
>  
>  If that works, time for another round of bisection, I guess!

I am not 100% sure, but it might be
https://mail-index.netbsd.org/source-changes/2024/03/25/msg150542.html
, however I don't see where aes_sse2_selftest() or 
aes_sse2_xts_update_selftest() might be calling snprintb().

There might also be some undefined behavior involved somewhere as not
every boot panics - it's hard to say how often it happens, but I'd put
it at around p=50%.  With a source tree from just before that change I
have so far not encountered this panic a single time.

So, I'd say your patch has improved things but the snprintb() issue
also needs to be addressed.


thanks,
  Harold