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Sat, 24 Oct 2026 22:45:12 -0700 (PDT) Received: from MalHyuk.localdomain ([211.201.32.99]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3adebb75254sm2620167a91.4.2026.10.24.22.45.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 24 Oct 2026 22:45:11 -0700 (PDT) From: "JongHyuk Kim(MalHyuk)" To: stable@vger.kernel.org Cc: JongHyuk Kim , Hyunwoo Kim , Andrew Morton , Lorenzo Stoakes , David Hildenbrand , linux-mm@kvack.org Subject: Please backport aedf2efd1897 ("mm/pagewalk: fix stale walk->action escaping walk_pmd_range()") to 6.12.y Date: Sun, 25 Oct 2026 14:45:05 +0900 Message-ID: <20261025054505.1448278-1-malhyuk97@gmail.com> X-Mailer: git-send-email 2.43.0 X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: ECCA320003 X-Stat-Signature: d5rw8d7zfcmd1n8aitbozw6q8491jgdu X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792907113-809184 X-HE-Meta: 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 J1Ie0Fsh W073xclQV6qI3g9LvcCeA7/iioxgpTuvjYv1Ti6fossbtO8qcJ60DKKWPDIVaC0fPGJmt/R/LXAGXdsatbg6G7VKQLtXbtAgtO8EoWEGg4NVwC1ahQPOXhMaw2t79PAYPgP/Y+Ibld/xpi+Qfw9eAsA2TgYCsfGtXEqmoXAvXf/sxRBRBZqTZH2UzO3cky+WidGDFYvpySTmiIGMSnaK5Mf5OY2hFpygAOIl4LSTfSW/22I8MbmfZZ2I7eDwWKyr3dAofhWRtx7er3TaUrtQvxAvmkqUCBoF78T94e1+I3OtXMTPm4mNUCzpo+CI78f3NGSngY+/niDdT7uhglTM5KMNbYe7wigM3NMZIDVa2Yy0euUsqpmOv9aQ/5dM1Kln7SRJd/uQr87d6VQ9XH2bHDXf4x1mf2jT/Yhc4UKRxl42rASBD1vPWHjFcCg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Please consider aedf2efd1897 ("mm/pagewalk: fix stale walk->action escaping walk_pmd_range()") for 6.12.y. It fixes 3b89863c3fa4 ("mm/pagewalk: fix race between concurrent split and refault"), which is in 6.12.y, but the fix has no Cc: stable so it was never picked up. 6.12.112 and 6.12.113 still have the pre-fix layout: in walk_pmd_range() the "walk->action = ACTION_SUBTREE" assignment sits below the pmd_none() block, so the continue in that block skips it and a stale ACTION_AGAIN survives into walk_pud_range(), which then re-walks the whole PUD with walk->private never reset. Same thing in walk_pud_range(). I hit it on the stock 6.12.112 KASAN build: BUG: KASAN: use-after-free in __mincore_unmapped_range+0x1ca/0x240 Write of size 1 at addr ffff888105ae2000 by task exp_root/191 CPU: 0 UID: 1000 PID: 191 Comm: exp_root Not tainted 6.12.112-dirty #1 __mincore_unmapped_range+0x1ca/0x240 mincore_unmapped_range+0x5d/0xd0 walk_pgd_range+0x8b0/0x1b10 __walk_page_range+0x418/0x600 walk_page_range+0x2b1/0x620 do_mincore+0x1a1/0x350 __x64_sys_mincore+0x1aa/0x390 The -dirty suffix comes from the kernelCTF build, the tree itself is unmodified 6.12.112. Reproducer shape, everything unprivileged (uid 1000): map a memfd so that a mincore() range of 4096 pages straddles a 1G boundary with exactly one PMD past the boundary, have a second process call MADV_COLLAPSE on that PMD so collapse_file() -> retract_page_tables() clears the PMD without holding mmap_lock, and spin on mincore() in the first process. The raced PMD has to be the last one in the range, otherwise the next non-none PMD resets walk->action and the leak is lost. It takes about a minute on a 2 vCPU guest. I can send the .c off-list if that is useful. Note that 6.12.y has no CONFIG_PT_RECLAIM, so the MADV_DONTNEED path used by CVE-2026-89754 does not reach this on 6.12, but MADV_COLLAPSE does. I only checked 6.12.y. Any stable tree that carries 3b89863c3fa4 without aedf2efd1897 should be in the same state. Thanks, JongHyuk Kim(MalHyuk)