linux-hardening - inconsistence in mprotect_fixup mlock_fixup madvise_update

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Message-ID: <CABi2SkWx_BnEHzGqqqbDMJi+vi-5a7XkQUCkyesN5PUtk23SgQ@mail.gmail.com>
Date:   Mon, 12 Jun 2023 18:04:39 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     linux-mm@...ck.org, linux-hardening@...r.kernel.org
Subject: inconsistence in mprotect_fixup mlock_fixup madvise_update_vma

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