linux-hardening - Re: inconsistence in mprotect_fixup mlock_fixup madvise_update

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Date:   Tue, 13 Jun 2023 08:26:26 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     linux-mm@...ck.org, linux-hardening@...r.kernel.org,
        Liam.Howlett@...cle.com, peterx@...hat.com,
        zhangpeng.00@...edance.com, akpm@...ux-foundation.org,
        koct9i@...il.com, david@...hat.com, ak@...ux.intel.com,
        hughd@...gle.com, emunson@...mai.com, rppt@...ux.ibm.com,
        aarcange@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: inconsistence in mprotect_fixup mlock_fixup madvise_update_vma

+ more ppl to the list.

On Mon, Jun 12, 2023 at 6:04 PM Jeff Xu <jeffxu@...omium.org> wrote:
>
> Hello,
>
> There seems to be inconsistency in different VMA fixup
> implementations, for example:
> mlock_fixup will skip VMA that is hugettlb, etc, but those checks do
> not exist in mprotect_fixup and madvise_update_vma. Wouldn't this be a
> problem? the merge/split skipped by mlock_fixup, might get acted on in
> the madvice/mprotect case.
>
> mlock_fixup currently check for
> if (newflags == oldflags || (oldflags & VM_SPECIAL) ||
> is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm) ||
> vma_is_dax(vma) || vma_is_secretmem(vma))
>
> Should there be a common function to handle VMA merge/split ?
>
> Best
> -Jeff