From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Lance Yang <lance.yang@linux.dev>, akpm@linux-foundation.org
Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com,
liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com,
dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev,
kas@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/1] mm/huge_memory: simplify pgtable deposit detection
Date: Fri, 18 Sep 2026 13:09:29 +0200 [thread overview]
Message-ID: <c57d9d3d-c007-4cf0-be9a-321e6ae62aae@kernel.org> (raw)
In-Reply-To: <20260918031905.92493-1-lance.yang@linux.dev>
On 9/18/26 05:19, Lance Yang wrote:
>
> On Thu, Sep 17, 2026 at 04:13:59PM -0700, Andrew Morton wrote:
>> On Thu, 17 Sep 2026 13:40:15 +0800 Lance Yang <lance.yang@linux.dev> wrote:
>>
>>> Whether a PMD has a deposited PTE page table only depends on whether the
>>> architecture requires deposits or the VMA is anonymous.
>>>
>>> Implement this rule directly in vma_has_deposited_pgtable(), avoiding
>>> mistaking a non-anonymous raw PFN PMD for one with a deposit and attempting
>>> to withdraw a page table that was never deposited.
>>
>> A large part of my life is asking $LLM "what are the userspace-visible
>> runtime effects of this bug". Because NOBODY EVER TELLS ME!!!
>
> That's on me ... I trimmed too much from v1.
>
>> This time it says "Processes using PMD-sized raw PFN mappings can
>> trigger a kernel NULL-pointer dereference when the mapping is torn
>> down", which sounds kinda important if true.
>
> There is no known in-tree workload that triggers it, though. Mostly a
> defensive/simplifying change.
Yeah, it's not a fix.
--
Cheers,
David
next prev parent reply other threads:[~2026-09-18 12:04 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 5:40 [PATCH v2 1/1] mm/huge_memory: simplify pgtable deposit detection Lance Yang
2026-09-17 14:24 ` Kiryl Shutsemau
2026-09-17 15:27 ` David Hildenbrand (Arm)
2026-09-17 15:29 ` Zi Yan
2026-09-17 23:13 ` Andrew Morton
2026-09-18 3:19 ` Lance Yang
2026-09-18 11:09 ` David Hildenbrand (Arm) [this message]
2026-09-18 8:34 ` Baolin Wang
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