linux-hardening - Re: [PATCH 0/6] Memory Mapping (VMA) protection using PKU

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Message-ID: <CABi2SkU9iDqpcXfPpwphEgL0-rBionphfT3+Zscq_Htx=ps+2g@mail.gmail.com>
Date:   Wed, 31 May 2023 16:02:00 -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,

Regarding siglongjmp:

On Thu, May 18, 2023 at 8:37 AM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 5/17/23 16:48, Jeff Xu wrote:
> > However, there are a few challenges I have not yet worked through.
> > First, the code needs to track when the first signaling entry occurs
> > (saving the PKRU register to the thread struct) and when it is last
> > returned (restoring the PKRU register from the thread struct).
>
> Would tracking signal "depth" work in the face of things like siglongjmp?
>
siglongjmp is interesting, thanks for bringing this up.

With siglongjmp, the thread doesn't go back to the place where signal is
raised, indeed, this idea of tracking the first signaling entry
doesn't work well with siglongjmp.

Thanks for your insight!
-Jeff


-Jeff