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Thu, 27 Aug 2026 22:59:47 -0700 (PDT) Received: from localhost.localdomain ([240e:b8f:1df9:a600:c693:b19f:ada0:748]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-396b0ea808csm5826241a91.2.2026.08.27.22.59.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2026 22:59:46 -0700 (PDT) From: Vernon Yang To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org Cc: 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, stable@vger.kernel.org, Vernon Yang Subject: [PATCH v4 0/3] mm: khugepaged: fix tracepoint UAF Date: Fri, 28 Aug 2026 13:59:23 +0800 Message-ID: <20260828055926.346744-1-vernon2gm@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DAA6DC0007 X-Stat-Signature: t67mjq7yzxt5yeh5wkcw3ig8a1fxi91c X-HE-Tag: 1787896788-428654 X-HE-Meta: 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 EjE1Fc1S JUMhPxR4R38HkLSVZ3npsxZ2pJcb113ujHF8LVwdBlXQFesjVTw8TqXqKx8sws7jpVExEsFyW7WoS9ulxaQencc+Qj5svqr7pyCSYjdk8MVdpENHQyD9HtPz0UvZqUvayYMw50Yi/9t29MKvYJxFkKESHlDEajkZD878pyIMpanS/Ti1vWLlKhWU2U5KstRp6N9WN+eIY9XpvEC2ukqEDdxAU1N7gj8rdLYOijyuFd8NiQldgIIxlBVWeEjC1W3eyfwDYDWElA6T2WRKUSsmftbsKgvUd5URMuSgJglIQFMG2DUVJFjk3KoN8n7in1sy7jYBbd6MdDMGQxcpdWMT1KxpOCAwY7St/1/rXwJ6qD8wn5uyH1Uql0kWLOXoFhf0cJfPIzkiCkrPq4NNpdg2mWt+MTA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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(). This series is based on mm-new. V3 -> V4: - Only trace the PFN if it really was problematic. - Calling the respective trace_xxx() functions separately on success and failure. - Set new_pfn once after successful alloc_charge_folio(). V2 -> V3: - Place folio_pfn() inside the xas_for_each() loop in PATCH#1. - Already defaulted the pfn value to -1, to simple it in PATCH#2. V1 -> V2: - Instead of passing the folio, just pass the pfn directly. - Using the folio_pfn() before dropping the reference or the page table lock. V3 : https://lore.kernel.org/linux-mm/20260824092935.73892-1-vernon2gm@gmail.com/ V2 : https://lore.kernel.org/linux-mm/20260815051924.194810-1-vernon2gm@gmail.com/ V1 : https://lore.kernel.org/linux-mm/20260811133655.267739-1-vernon2gm@gmail.com/ Vernon Yang (3): mm: khugepaged: fix swap entry value to folio_pfn() mm: khugepaged: fix folio is used after pte_unmap_unlock() mm: khugepaged: fix folio is used after folio_put/unlock() include/trace/events/huge_memory.h | 18 ++++++++--------- mm/khugepaged.c | 32 +++++++++++++++++++++++++----- 2 files changed, 36 insertions(+), 14 deletions(-) base-commit: 1a46b1e97bde62afa7d925bb0dcd9f9748a1d7c3 -- 2.53.0