lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CABi2SkVmAw379G-o26sZnmt5p2FY8atoDfRMfKv0yFsfJOe7rA@mail.gmail.com>
Date:   Wed, 31 May 2023 18:39:00 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Jeff Xu <jeffxu@...gle.com>,
        Stephen Röttger <sroettger@...gle.com>,
        luto@...nel.org, jorgelo@...omium.org, keescook@...omium.org,
        groeck@...omium.org, jannh@...gle.com, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-mm@...ck.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 0/6] Memory Mapping (VMA) protection using PKU - set 1

Hi Dave,
Thanks for feedback, regarding sigaltstack:

On Thu, May 18, 2023 at 2:04 PM Dave Hansen <dave.hansen@...el.com> wrote:
> >
> > Agreed on signaling handling is a tough part: what do you think about
> > the approach (modifying PKRU from saved stack after XSAVE), is there a
> > blocker ?
>
> Yes, signal entry and sigreturn are not necessarily symmetric so you
> can't really have a stack.
>

To clarify: I mean this option below:
- before get_sigframe(), save PKUR => tmp
- modify thread's PKRU so it can write to sigframe
- XSAVE
- save tmp => sigframe

I believe you proposed this in a previous discussion [1]:
and I quote here:
"There's a delicate point when building the stack frame that the
kernel would need to move over to the new PKRU value to build the
frame before it writes the *OLD* value to the frame.  But, it's far
from impossible."

sigreturn will restore thread's original PKRU from sigframe.
In case of asymmetrics caused by siglongjmp, user space doesn't call
sigreturn, the application needs to set desired PKRU before siglongjmp.

I think this solution should work.

[1] https://lore.kernel.org/lkml/b4f0dca5-1d15-67f7-4600-9a0a91e9d0bd@intel.com/

Best regards,
-Jeff

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ