From: Ryan Roberts <ryan.roberts@arm.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Zi Yan <zi.yan@cs.rutgers.edu>,
"Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2] arm64/mm: pmd_mkinvalid() must handle swap pmds
Date: Wed, 1 May 2024 09:05:17 +0100 [thread overview]
Message-ID: <e0624ca9-b321-479e-9b64-59a4cd242f6d@arm.com> (raw)
In-Reply-To: <171449974870.639201.3165060270571039049.b4-ty@arm.com>
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?
>
> [1/1] arm64/mm: pmd_mkinvalid() must handle swap pmds
> https://git.kernel.org/arm64/c/e783331c7720
>
next prev parent reply other threads:[~2024-05-01 8:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 13:31 [PATCH v2] arm64/mm: pmd_mkinvalid() must handle swap pmds Ryan Roberts
2024-04-30 13:55 ` Will Deacon
2024-04-30 14:04 ` Ryan Roberts
2024-04-30 16:23 ` Catalin Marinas
2024-04-30 16:25 ` Ryan Roberts
2024-04-30 15:00 ` Zi Yan
2024-04-30 17:57 ` Catalin Marinas
2024-05-01 8:05 ` Ryan Roberts [this message]
2024-05-01 10:04 ` Catalin Marinas
2024-05-01 10:13 ` Ryan Roberts
2024-05-02 18:00 ` Catalin Marinas
2024-05-01 11:35 ` Ryan Roberts
2024-05-01 11:38 ` Ryan Roberts
2024-05-01 12:07 ` Zi Yan
2024-05-01 12:58 ` Ryan Roberts
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