Messages in this thread | | | Date | Mon, 30 Jan 2023 10:08:14 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() |
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On Fri, Jan 27, 2023 at 03:16:52PM +0000, 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.
FWIW, that hasn't hit anything so far.
It would be good if we could explicitly nots which mm test suite and/or stress tests are happy with this, but otherwise this looks good to me.
Thanks, Mark.
> 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. > > Thanks, > Mark.
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