From: Lance Yang <lance.yang@linux.dev>
To: vernon2gm@gmail.com
Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org,
nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com,
baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev,
zokeefe@google.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2 0/3] mm: khugepaged: fix tracepoint UAF
Date: Sun, 16 Aug 2026 01:44:44 +0800 [thread overview]
Message-ID: <20260815174444.4164-1-lance.yang@linux.dev> (raw)
In-Reply-To: <20260815051924.194810-1-vernon2gm@gmail.com>
On Sat, Aug 15, 2026 at 01:19:21PM +0800, Vernon Yang wrote:
>From: Vernon Yang <yanglincheng@kylinos.cn>
>
>The khugepaged tracepoints take a folio pointer and call folio_pfn(),
>but by then the folio may no longer be valid: freed after folio_put(),
>folio_unlock() or pte_unmap_unlock(), or not a folio at all but an
>xarray-encoded swap entry. On classic SPARSEMEM, dereferencing it oopses
>khugepaged as soon as the trace event is enabled; on other memory models
>it merely prints a bogus pfn.
>
>Pass the pfn to the tracepoints directly, captured while the folio is
>still pinned, closing the use-after-free windows in
>mm_khugepaged_scan_file(), mm_khugepaged_scan_pmd() and
>mm_khugepaged_collapse_file().
Well spotted!
Gave the series a run on x86_64 (KVM), all good (only classic SPARSEMEM
untested) :)
Tested-by: Lance Yang <lance.yang@linux.dev>
next prev parent reply other threads:[~2026-08-15 17:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-15 5:19 [PATCH v2 0/3] mm: khugepaged: fix tracepoint UAF Vernon Yang
2026-08-15 5:19 ` [PATCH v2 1/3] mm: khugepaged: fix swap entry value to folio_pfn() Vernon Yang
2026-08-15 5:19 ` [PATCH v2 2/3] mm: khugepaged: fix folio is used after pte_unmap_unlock() Vernon Yang
2026-08-15 5:19 ` [PATCH v2 3/3] mm: khugepaged: fix folio is used after folio_put/unlock() Vernon Yang
2026-08-15 17:44 ` Lance Yang [this message]
2026-08-15 18:16 ` [PATCH v2 0/3] mm: khugepaged: fix tracepoint UAF Lance Yang
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