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 C6008606A32C for ; Mon, 26 Oct 2026 23:29:11 +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=fj+FyqJR; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=UNbUEG/S 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:Cc:To:In-Reply-To:References :Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From: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=OoFHaYBhm5BDHRt4hk2dDlai0Lu5WpyAocva34cAfYA=; b=fj+FyqJRRCIxLJ vFQPiLrePh6YNGTXo83z8i5u6zxDzZqtuBO5ll3bl2G4FrU0mkXzNyVnXXIZDE1h3NKxuNtOYP4bu bHfUDetn+hYAA42OIs8YMIa0B0wbgOZauLMaGEiIpYBvy/GcUTo+3AlGxFpXD9LSXAxecZJk79c/4 uRkcdbe9UwMKIsgt/dqEk4AVOCq9O/qvnbRJgiQu4jMjhU1QjOil8Ow0bJ2Rq4y1rKD8pTnahl3rn t9xV9sxCIkefsPIduXvPr5JkJjQFc9966HadizH7i/p8Mh+AKJzyRkN2aS1O5stqtSdQHX8cLQQiu ovvAFdsu2zfP1C0k1W9g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLU7r-00000003RV6-2Dak; Mon, 26 Oct 2026 23:29:11 +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 1xLU7q-00000003RV0-1Kgv for kexec@lists.infradead.org; Mon, 26 Oct 2026 23:29:10 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 09B454146D; Mon, 26 Oct 2026 23:29:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B0091F01825; Mon, 26 Oct 2026 23:28:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057349; bh=OoFHaYBhm5BDHRt4hk2dDlai0Lu5WpyAocva34cAfYA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=UNbUEG/SujRxvLabLs1Ob9p21oBhi+rGXvfUKjqMDQc12IUiZnwmTDApSDiN/doHK Htp9Ipsw+SQp+pFzIORI8kLx2XLdu4rOahJ0TPlelHfX1GJ1qLDkN8+N+aWCn8WCds tZKLfzo3kEI2Ic5a7yAs64WNXkp0GQ9463s7JB2V/ciJHVqOo5idW1iS2SKYE4l3o+ mmQ3vIfL+tDLHRHgEyxeKpggddER2NA819TKZnVHtRhi+Sq3NPEIiR5ET0FwgZX6ei fEZXbzJhICbnx1enS+A8NU5WTSrME8TXg/tsHJn7ecpC43Su1OH1tQwLJM8cp/lhBz YEOm5b5Nlxakg== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:56 +0100 Subject: [PATCH 36/46] mm: fix unkillable fault loop on MAP_DROPPABLE memory X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261027-fixes_core-v1-36-6f74bec9a5bb@kernel.org> References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> In-Reply-To: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> To: 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 , Pedro Falcato , 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 Cc: 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, Chris Mason , stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1689; i=david@kernel.org; h=from:subject:message-id; bh=pzxM/cFKO4VXQWnP1gi4l+XWqAOEVbNka7bwCiIYBW0=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu358ufnWFRtyuxz0v7f0W/Xstsp+rpij0whZOtoAdj O+fvJVI6ShlYRDjYJAVU2QJCr5v8PLlutpqNz5mmDmsTCBDGLg4BWAipR2MDJPYqpQSJzxd+VjV Sur4qftq4hcCTkXs/XHuWWzbsvvV/zwZGT7UT1FdZiUx0a1TNyc2/fYVjS1HumMsfZ2tf/o2Fkz IZgcA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 From: Chris Mason handle_mm_fault() suppresses VM_FAULT_OOM for VM_DROPPABLE mappings. For user-mode faults, pending signals are processed before retrying the access. Kernel-mode faults on user buffers instead return directly to the faulting instruction. With persistent allocation failures (esp. memcg limits), a syscall, such as write(), can therefore loop while not dropping locks. Only suppress VM_FAULT_OOM when FAULT_FLAG_USER is set, allowing kernel-mode faults and GUP to fail and signal allocation errors. Fix generated by an LLM and sent by Chris Mason in private. Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Reviewed-by: Lorenzo Stoakes (ARM) [ david: simplify description ] Signed-off-by: David Hildenbrand (Arm) --- mm/memory.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 5c5f326b8bcbe..230a2f4dafa13 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6957,8 +6957,12 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, lru_gen_exit_fault(); - /* If the mapping is droppable, then errors due to OOM aren't fatal. */ - if (is_droppable) + /* + * If the mapping is droppable, then errors due to OOM aren't fatal: the + * task returns to user mode, handles its signals and tries again. A + * fault from kernel mode has no such return, so it must see the error. + */ + if (is_droppable && (flags & FAULT_FLAG_USER)) ret &= ~VM_FAULT_OOM; if (flags & FAULT_FLAG_USER) { -- 2.43.0