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Sat, 15 Aug 2026 17:44:53 +0000 X-Migadu-Flow: FLOW_OUT From: Lance Yang 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 Message-Id: <20260815174444.4164-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260815051924.194810-1-vernon2gm@gmail.com> References: <20260815051924.194810-1-vernon2gm@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: AED5C20002 X-Stat-Signature: au6ejuwp7ce9xrcy59qcgejt87y6qd7f X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1786815895-866147 X-HE-Meta: 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 4Bkmlk1Z BAktZiREzct3EXZ3fGrQGoV+LoANtEdyjkitBIzrS2OWNXnl7F83RyP+vJ5sNXG88rrtiOxvaO3vryI7b3CDSQRArqCKI8ybP1atBUiNzXyf90P4Tpu6Yh1BmeNNGvkstcKpbMJIylYyCjv+3BaWYHCwp4jUhveIH8FQgWyDOAG160hGcDj9hIV/ALhlmE93ZHxUk9lIaqozDSrEu7i3wxT93N3KmNrNQiN49Os0rI4igGZNj8DjhZbWL2xItHA9TvuTfyd2KUR9jNqcrKAQ2am9EvRhL4RN3mjdZ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, Aug 15, 2026 at 01:19:21PM +0800, Vernon Yang wrote: >From: Vernon Yang > >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