linux-kernel - Re: mprotect outbound check.

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Message-ID: <CABi2SkUfsOWKGdFqgXZg=0AcnUj=AOFb9JmYfp=RwDp_5AcH0Q@mail.gmail.com>
Date:   Mon, 15 May 2023 18:41:35 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, linux-hardening@...r.kernel.org,
        Jorge Lucangeli Obes <jorgelo@...omium.org>,
        lstoakes@...il.com, Liam.Howlett@...cle.com, peterx@...hat.com,
        zhangpeng.00@...edance.com
Subject: Re: mprotect outbound check.

+ Peter, Lian, Lorenzo

Is this related to this hotfix ?
      mm/mprotect: fix do_mprotect_pkey() return on error


Thanks!

-Jeff






On Mon, May 15, 2023 at 11:00 AM Jeff Xu <jeffxu@...omium.org> wrote:
>
> Noticed there is a slight change for mprotect between 6.1 and 6.4 RC1
>
> For example:
> Consider the case below:
> 1 mmap(0x5000000, PAGE_SIZE,  ...)
> 2 mprotect(0x5000000, PAGE_SIZE*4, ...)
>
> in 6.1 and before, 2 will fail, and in 6.4 RC1, it will pass.
>
> I know that munmap will accept out-of-bound cases like this (because
> memory is freed anyway).
>
> Is this change intentional ?
>
> Thanks!
> Best regards,
> -Jeff