From: Lance Yang <lance.yang@linux.dev>
To: akpm@linux-foundation.org
Cc: lance.yang@linux.dev, david@kernel.org, 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 11:19:05 +0800 [thread overview]
Message-ID: <20260918031905.92493-1-lance.yang@linux.dev> (raw)
In-Reply-To: <20260917161359.9ba88d2bcab42db8111130e1@linux-foundation.org>
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.
>Help me out here?
>
>Also, thanks ;)
Thanks!
prev parent reply other threads:[~2026-09-18 3:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 5:40 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 [this message]
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