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From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
To: "David Hildenbrand (Arm)" <david@kernel.org>
Cc: Zhao Gongyi <zhaogongyi@bytedance.com>,
	akpm@linux-foundation.org,  xu.xin@linux.dev,
	chengming.zhou@linux.dev, aarcange@redhat.com, riel@redhat.com,
	 linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/ksm: avoid anon_vma UAF during page merging
Date: Mon, 2 Nov 2026 11:23:43 +0000	[thread overview]
Message-ID: <auhyO_ZZ5fFYvjOi@gremlin> (raw)
In-Reply-To: <79820b33-7e74-4e12-926f-1e03987d7bda@kernel.org>

On Sun, Nov 01, 2026 at 07:11:25PM +0100, David Hildenbrand (Arm) wrote:
> On 10/31/26 19:22, Zhao Gongyi wrote:
>
> Hi,
>
> thanks for the report! CCing Lorenzo.
>
> > KASAN reports a use-after-free in page_address_in_vma() while ksmd
> > merges pages. ksmd keeps a folio reference across an mmap_lock drop,
> > during which mremap() can remove its last mapping and free its
> > anon_vma. page_address_in_vma() then dereferences the stale pointer
> > from folio->mapping.

Fun fun. KSM is dropping the lock then assuming the VMA doesn't change.

I want to take a different approach to this fix so I'll take it over.

>
> Do you have a link to the report or the actual KASAN report?

Thanks, the attached report is useful.

--
Cheers, Lorenzo

  parent reply	other threads:[~2026-11-02 11:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-10-31 18:22 Zhao Gongyi
2026-11-01 18:11 ` David Hildenbrand (Arm)
2026-11-02  3:32   ` Zhao Gongyi
2026-11-02 11:23   ` Lorenzo Stoakes (ARM) [this message]
2026-11-02 10:18 ` xu.xin
2026-11-02 11:14   ` Zhao Gongyi
2026-11-02 12:14   ` Lorenzo Stoakes (ARM)

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