Messages in this thread | | | Date | Thu, 26 Jan 2023 13:33:22 +0000 | From | Will Deacon <> | Subject | Re: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() |
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On Tue, Jan 24, 2023 at 11:11:49AM +0530, Anshuman Khandual wrote: > On 1/9/23 10:58, Anshuman Khandual wrote: > > Changing pfn on a user page table mapped entry, without first going through > > break-before-make (BBM) procedure is unsafe. This just updates set_pte_at() > > to intercept such changes, via an updated pgattr_change_is_safe(). This new > > check happens via __check_racy_pte_update(), which has now been renamed as > > __check_safe_pte_update(). > > > > Cc: Catalin Marinas <catalin.marinas@arm.com> > > Cc: Will Deacon <will@kernel.org> > > Cc: Mark Rutland <mark.rutland@arm.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > > --- > > This applies on v6.2-rc3. This patch had some test time on an internal CI > > system without any issues being reported. > > Gentle ping, any updates on this patch ? Still any concerns ?
I don't think we really got to the bottom of Mark's concerns with unreachable ptes on the stack, did we? I also have vague recollections of somebody (Robin?) running into issues with the vmap code not honouring BBM.
So I think we should confirm/fix the vmap issue before we enable this check and also try to get some testing coverage to address Mark's worries. I think he has a syzkaller instance set up, so that sound like a good place to start.
Will
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