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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: k33k7w3p1zrhthybsegazsjrgawjydab X-Rspamd-Queue-Id: 34365C0015 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1714558422-225481 X-HE-Meta: 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 cRJ9kXbX Ge7jo4eTBDpfLKzhD8qDu2lnbkf+cH/SWm+s7ndfCcPj25w4FhktDVz8YMwlj2tWTiGx/aKCxgsjj8DhB6+FigKX9VZGIUZprIxfO+4gk1PZgJKzx3FPbTJ2J5gQyDY6NQbYdQEyH7zpeDC7ASK0e1agADvCg0+/DkKIPH3PjoVzyUe3DzQ8Fmig6j+ztzVp6MHLh X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 01/05/2024 11:04, Catalin Marinas wrote: > On Wed, May 01, 2024 at 09:05:17AM +0100, Ryan Roberts wrote: >> On 30/04/2024 18:57, Catalin Marinas wrote: >>> On Tue, 30 Apr 2024 14:31:38 +0100, Ryan Roberts wrote: >>>> __split_huge_pmd_locked() can be called for a present THP, devmap or >>>> (non-present) migration entry. It calls pmdp_invalidate() >>>> unconditionally on the pmdp and only determines if it is present or not >>>> based on the returned old pmd. >>>> >>>> But arm64's pmd_mkinvalid(), called by pmdp_invalidate(), >>>> unconditionally sets the PMD_PRESENT_INVALID flag, which causes future >>>> pmd_present() calls to return true - even for a swap pmd. Therefore any >>>> lockless pgtable walker could see the migration entry pmd in this state >>>> and start interpretting the fields (e.g. pmd_pfn()) as if it were >>>> present, leading to BadThings (TM). GUP-fast appears to be one such >>>> lockless pgtable walker. >>>> >>>> [...] >>> >>> Applied to arm64 (for-next/fixes), thanks! It should land in 6.9-rc7. I >>> removed the debug/test code, please send it as a separate patch for >>> 6.10. >> >> Thanks Catalin! I'm guessing this will turn up in today's linux-next, so if I >> send the tests today and Andrew puts them straight in mm-unstable (which will >> goto linux-next) there is no risk that the tests are there without the fix? Or >> do I need to hold off until the fix is in v6.9-rc7? > > It looks like we don't push for-next/fixes to linux-next, it's > short-lived usually, it ends up upstream quickly. I can send the pull > request later today, should turn up in mainline by tomorrow. You can add > a note to your patch for Andrew that it will fail on arm64 until the fix > ends up upstream. It's a matter of a couple of days anyway. OK, I just didn't want to send it only for our CI to start failing. I'll do as you suggest.