From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5F319606A329 for ; Tue, 27 Oct 2026 19:18:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=KcYC35oZ; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=YLTdJU5x DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=RZNM0QAvkjv2toljsz6cT0DUeLHvWGObkljY6MMux0Q=; b=KcYC35oZE/K9S2 2pOzeaYK16SesVrxbq5yVdF70wid+Mr4TfhqnKeT3BxNeQdI5C1KIbzOtvOjA2Kscty0O5OwAooLI 0t2v+G6ZZQ4mFvuUR9PFWtwiwwrXxdBYQ1dCmAPlHExZtaGHI0/ZHZJj6jeJCV6eaTn337Q+guXh3 dL1qsil1Pe/s5asT14NER1o3lpkcTlE1vfjdkFlb/yChRhr8M9ZMZZDHOkMSIPI0PaHcmm/iH+kzO XKOuEb8FefHu2aYZXroY9vPhrYE9nXAMvbA5pkePbs6l+lSMBZQJal0ubWChTqnuwNwCM+bjg/I5G rPZagqnv9tJU2vJe3h6A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLmgt-00000005dR5-3zhQ; Tue, 27 Oct 2026 19:18:35 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLmgt-00000005dQx-0yOF for kexec@lists.infradead.org; Tue, 27 Oct 2026 19:18:35 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id A989140A09; Tue, 27 Oct 2026 19:18:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16F571F01828; Tue, 27 Oct 2026 19:18:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793128714; bh=RZNM0QAvkjv2toljsz6cT0DUeLHvWGObkljY6MMux0Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=YLTdJU5x4o/hyyOxOFwqDIU1Y1ZNR6KV42KTsOrPC3aE7fsc7yxHnDHmlusk1ZAbc 7WbghDU5l1NvCkEtJodjasUhWzXCgfr9Vha9UktQimiDcYzzLg0LinN4/zyoZDs/d3 xfVJdoPYVZikMrjRBlxg3rIShOQQ8xtdT4qpb5cOTugMevkB5DTpGK+9lx5QKKrr3s RyHvkSeezsGEWBuWOGF0Wz9rAaW4YKD2jM7O1WA/e7eicq1Lz93J6oO28CTPO/D4Pd RVDg5X3Wj+ZwE0ZbdDEia09ullo9NdzzRIZxY/uH0ERFDqHqyUI36UAodcWUnV9aDO Dxn7IlIn18beQ== Message-ID: <11b91d57-85e6-47d0-87ab-5fa8624e8068@kernel.org> Date: Tue, 27 Oct 2026 20:18:18 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 07/46] mm/filemap: don't lose a folio lock wakeup to a signal To: Pedro Falcato Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Dev Jain , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe , 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 Bacik , stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-7-6f74bec9a5bb@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/27/26 17:10, Pedro Falcato wrote: > On Tue, Oct 27, 2026 at 12:17:27AM +0100, David Hildenbrand (Arm) wrote: >> From: Josef Bacik >> >> An exclusive waiter in folio_wait_bit_common() can leave the wait loop >> because of a fatal signal, then be woken by folio_unlock() before >> finish_wait(). If the waker did not hand over the lock, the waiter returns >> -EINTR without trying to acquire it. >> >> folio_wake_bit() stops after waking the first exclusive waiter, so this >> loses the wakeup and can leave other waiters asleep indefinitely on an >> unlocked folio. >> >> After finish_wait(), let a waiter woken without a lock handoff try once >> more to acquire the lock. If successful, return success so the caller's >> eventual unlock wakes the next waiter. Otherwise, the current lock owner >> will do so. > > Has this been reproduced? I feel like this would've been found out by now? Let me dig ... I don't find mention in the notes, but I was told that most of these things have reproducers. I guess it's harder to hit in practice, because you need a fatal signal and then keep the other waiter alive while nobody else will take that lock in a timely fashion. I asked codex to try writing one but it refuses for security reasons :) -- Cheers, David