From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5F4CE606A32A for ; Mon, 26 Oct 2026 23:29:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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 Received: by kanga.kvack.org (Postfix) id 632BA6B05B1; Mon, 26 Oct 2026 19:29:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 60A186B05D7; Mon, 26 Oct 2026 19:29:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4F9776B05F5; Mon, 26 Oct 2026 19:29:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 2BF4F6B05B1 for ; Mon, 26 Oct 2026 19:29:13 -0400 (EDT) Received: from smtpin29.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 9A4D71C429B for ; Mon, 26 Oct 2026 23:29:12 +0000 (UTC) X-FDA: 85366370544.29.CE07AA4 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf24.hostedemail.com (Postfix) with ESMTP id B77C4180003 for ; Mon, 26 Oct 2026 23:29:10 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="UNbUEG/S"; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793057350; b=zRNsf2RiIFPOV+vxn/N9XzGFVjamlSl273SvpJdBwNUBgVsh+fruFCJ9Pmw5zxK/4TxO2L PHV+eGq1LKaJizpK2PwxhPd3bEYi5DkDtaTQ97/FL0uptWbqNUzWA8pN4B1lGbwP5YnLTA XrIJWUL61aAEZe0Hxbi8ElAyyHLf7to= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="UNbUEG/S"; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793057350; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=OoFHaYBhm5BDHRt4hk2dDlai0Lu5WpyAocva34cAfYA=; b=jBdZ20HBT3lfXQu1Mz1yZGtRGsdJmK4qQNmcoaD7b3ub4lOAXDGst+gRHoUSiBBqTUJqx4 dW93bgyoEun3nqHsQwK9BKX4gHae2vb9Xl7Awv7qutxL8twE2/y7V9Kc/FKL9ieR91u2K+ V0OdB35mL+RP9u1ZmGNugLe8bnSJ/WA= 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-Stat-Signature: asj6iw7ay1yyif6mcx76uqit4eckr5am X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B77C4180003 X-Rspam-User: X-HE-Tag: 1793057350-557894 X-HE-Meta: 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 +DmW4ilT BzQoRJXJQurFLEEupTvzJyO2kowJ4io+utFQ1P447qpvGVOtlBu384yILJgKHdA7cKT38xgoOLRYMLdF55dblFwON1OrJ39SIhDAmI+0iSAFxzRp6dvV/iZ9lplfwea7FyCdEu9x6R2Z3ybfZ08JOyexNunbuWDYOx0PWBCBXhXEKRB6Naj/LpCr97dIGs0Ee7I+jIFDTWXIG7v4KXKrI+/qyYR7zLR8ajX3Z8pIiC7xzJzECal6CH5phmpNqniMS741GnGS+cAivxpvohuR7/lY/6SYW0hbMpyVzM/NDZr+MaBY1kFBUVcLEr06yTKMQ14LlpJJlgALNLpEHZWiK3M7Boa3HF8cVR9/0quHiNM9HAUs= 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 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