Messages in this thread | | | Date | Mon, 30 Jan 2023 13:46:10 +0530 | Subject | Re: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() | From | Anshuman Khandual <> |
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On 1/27/23 20:46, Mark Rutland wrote: > On Thu, Jan 26, 2023 at 01:33:22PM +0000, Will Deacon wrote: >> 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. > > I've thrown my Syzkaller instance at this patch; if it doesn't find anything by > Monday I reckon we should pick this up. > > That said, I had some minor nits on the patch; I'm not sure if you'd be happy > to apply the suggested changes when applying or if you'd prefer that Anshuman > applies those locally and sense a v3.
I could send out a V3, running some stress-ng based memory tests with the suggested changes applied on the patch.
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