From: Andrew Morton <akpm@linux-foundation.org>
To: mboone@akamai.com
Cc: Max Boone via B4 Relay <devnull+mboone.akamai.com@kernel.org>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v2] mm/pagewalk: fix race between concurrent split and refault
Date: Wed, 25 Mar 2026 17:50:06 -0700 [thread overview]
Message-ID: <20260325175006.1c3cae2ee50dd491a153226e@linux-foundation.org> (raw)
In-Reply-To: <20260325-pagewalk-check-pmd-refault-v2-1-707bff33bc60@akamai.com>
On Wed, 25 Mar 2026 10:59:16 +0100 Max Boone via B4 Relay <devnull+mboone.akamai.com@kernel.org> wrote:
> The splitting of a PUD entry in walk_pud_range() can race with
> a concurrent thread refaulting the PUD leaf entry causing it to
> try walking a PMD range that has disappeared.
>
> An example and reproduction of this is to try reading numa_maps of
> a process while VFIO-PCI is setting up DMA (specifically the
> vfio_pin_pages_remote call) on a large BAR for that process.
>
> This will trigger a kernel BUG:
> vfio-pci 0000:03:00.0: enabling device (0000 -> 0002)
> BUG: unable to handle page fault for address: ffffa23980000000
> PGD 0 P4D 0
> Oops: Oops: 0000 [#1] SMP NOPTI
Thanks, updated.
AI review has a couple of questions:
https://sashiko.dev/#/patchset/20260317-pagewalk-check-pmd-refault-v1-1-f699a010f2b3%40akamai.com
It flagged the same things against the v1 patch - maybe nobody checked?
next prev parent reply other threads:[~2026-03-26 0:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-25 9:59 [PATCH v2] mm/pagewalk: fix race between concurrent split and refault Max Boone via B4 Relay
2026-03-25 10:06 ` David Hildenbrand (Arm)
2026-03-25 15:14 ` Lorenzo Stoakes (Oracle)
2026-03-26 0:50 ` Andrew Morton [this message]
2026-03-26 8:42 ` David Hildenbrand (Arm)
2026-03-26 9:38 ` Boone, Max
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