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Mon, 02 Nov 2026 05:42:37 +0000 X-Mizu-Trace-ID: 9704e208af575192 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kees@kernel.org, peterz@infradead.org, jannh@google.com, pfalcato@suse.de, hughd@google.com, pasha.tatashin@soleen.com, pratyush@kernel.org, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, lance.yang@linux.dev, riel@surriel.com, harry@kernel.org, apopple@nvidia.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, jhubbard@nvidia.com, peterx@redhat.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, osalvador@suse.de, minchan@kernel.org, muchun.song@linux.dev, xu.xin@linux.dev, chengming.zhou@linux.dev, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, youngjun.park@lge.com, gourry@gourry.net, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, jgg@ziepe.ca, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, josef@toxicpanda.com, stable@vger.kernel.org, usama.anjum@arm.com Subject: Re: [PATCH v3 16/47] mm/khugepaged: fix PMD table lock leak in try_collapse_pte_mapped_thp() Date: Mon, 2 Nov 2026 13:42:32 +0800 Message-ID: <20261102054232.36829-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261031-fixes_core-v3-16-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-16-d6437171ecc3@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8433340004 X-Stat-Signature: ym8sct7sopyxz18a5cutni68x43s3tgf X-Rspam-User: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793598160-411441 X-HE-Meta: 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 hlKclQlF tLc4zcIed4Kd5itZmyVLM+accGxyJJgsE7kHmOoMgzWeE4uNCb1s3cfkuFyIe8ia4cE6S3d6Hqg3BKI77FQdojK1YqqeOZ1PobQuR9T44bK71e+7wS7t8xHCDl7P3kQlN+qYc0E9bjlOhSOcXntAD6QenONqZGjsXt775vf9Hc9Moo8LTB4emyxyAjgmukBrbUKnZ9g256pEOGjWd/fsEfLvDalnE9+XJ6VnytawXq2scsk0c2h/WMGb0VWmKvH8NJaozmtwa3tLcAXuU2Dj5+uM+pnLWJJZ5jDQrMimLTJc4sF1bqMOwjcCBAg7h0v9cIF7yijQeveCQ2gjjKlR/l9FgE3/Vzo6CQplp9x+tyuRIRG4ff+cYn7iOKFswr1NehRuWa91/QpyGrk3DoNQXwxSdxkmokQdSa5ntRKY81nGfS/MxeemgDQPxuJJ00IaC048MR3zDVZcU7OlAmq50Z1DsIK0YKT9rjeVtw9SvmYVhaY8tfSuXC3Ft7a+P5XVsUDdCDsqN5ZbqDuafFP0xJEZ5UhxU8bBDC18V2pjYcCaaI0QJrGZqPmobQw== 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 On Sat, Oct 31, 2026 at 10:39:45AM +0100, David Hildenbrand (Arm) wrote: >From: Josef Bacik > >For a private mapping with userfaultfd, try_collapse_pte_mapped_thp() >takes the PMD table lock before it maps the page table for the second time. >If that (pte_offset_map_rw_nolock) fails, because the page table vanished >in the meantime due to concurrent page table reclaim, it leaves through >the abort label, where the PMD table lock is unlocked if it differs from >PTE table lock. > >In case the PMD table lock and the PTE table lock match, which is the >case without CONFIG_SPLIT_PTE_PTLOCKS after pte_offset_map_rw_nolock() >failed, we miss to unlock the PMD table. > >To fix it, forget the PTE table lock when we unmap+unlock the PTE table. > >Fix generated by an LLM and sent by Josef Bacik in private. > >Fixes: 6375e95f381e ("mm: pgtable: reclaim empty PTE page in madvise(MADV_DONTNEED)") >Cc: stable@vger.kernel.org >Signed-off-by: Josef Bacik >[ david: move the ptl = NULL handling; rewrite description, drop wrong comments ] >Reviewed-by: Gregory Price (Meta) >Tested-by: Gregory Price (Meta) >Tested-by: Muhammad Usama Anjum >Signed-off-by: David Hildenbrand (Arm) >--- Reviewed-by: Lance Yang