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 92550606A31D for ; Sat, 31 Oct 2026 09:49:57 +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=h8uJy23m Received: by kanga.kvack.org (Postfix) id B9FCA6B05E8; Sat, 31 Oct 2026 05:49:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B4FA96B05E9; Sat, 31 Oct 2026 05:49:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A3EB56B05EA; Sat, 31 Oct 2026 05:49:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8219C6B05E8 for ; Sat, 31 Oct 2026 05:49:56 -0400 (EDT) Received: from smtpin23.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 1F3951408D3 for ; Sat, 31 Oct 2026 09:49:56 +0000 (UTC) X-FDA: 85382449992.23.F0F9F33 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf21.hostedemail.com (Postfix) with ESMTP id 4ACAF1C0004 for ; Sat, 31 Oct 2026 09:49:54 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h8uJy23m; spf=pass (imf21.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=1793440194; b=FyJKhOqOohIjV33oEJWxum13KF2NpiAoHXGrORoQvlgvFv9e9JEgr1I5BmfQwZcwympjSK 2JJ4Tns3nQaVP8I4GWZMXW2jOPHArghBUmogXiIY4kHWo6eMsvA9V1dMpdMUw0sip6CSP7 w76maF0DG8xboub6IoY9270OV2+YMzg= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=h8uJy23m; spf=pass (imf21.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=1793440194; 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=6KPzj8boSo2Gk3+3ECHnUsyvk9AxPiK+EOaIJxEN6Go=; b=ynLYyrcqfF85Q3+OorpWnImKhWfneuqFUw290hoSMfFQxuf9VPa3cLZZ2rBeb1Qd7IcT1K gB9xD0rYkkiCAsAGsroumVaZ2g0Wm4eq9IiLkF8AP17G3rrMBKElKWVNvNvOO6YnzekrY7 r6gmQlv30WWJEd7J3dyGPDyZsIXZNrI= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id D1D0C43588; Sat, 31 Oct 2026 09:49:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09AC41F00A16; Sat, 31 Oct 2026 09:49:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793440192; bh=6KPzj8boSo2Gk3+3ECHnUsyvk9AxPiK+EOaIJxEN6Go=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=h8uJy23m3iqMl3OwU/TM+eG06BDIlLaiL+p78gyW/VyxpuisHpa2ij0C+rNXmy/03 It3m3GuGtjE1NLJE7RvqGkdLdWj64TbEwTq+FK9jdAgAMRRLLG0OFvDhEHOXIwMmzh Ph+e2q0/8C3LArjv4DLBCBIlUpCi3pOHs2a+Gex1nTr7/Tp4pokf6D3HyAEdm+nENQ WR3Dc2oa2Y9tdNn0AJ7rqpEELD1qIZkhidc3x1iia2aUU7kmgloZMD6mGBIbvvHLue tnycJdnsNH7tD/BAWlohAJfDtEVTzqgdRhmAlOZgGnqWVujtbljH2p0m4ztc6FHdjv 3AMt5DmbFMxZQ== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:40:06 +0100 Subject: [PATCH v3 37/47] 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: <20261031-fixes_core-v3-37-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-0-d6437171ecc3@kernel.org> In-Reply-To: <20261031-fixes_core-v3-0-d6437171ecc3@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, Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1744; i=david@kernel.org; h=from:subject:message-id; bh=3QXuBW/o+aJfpqMh7L6nYMz0PgksViIVDVNcIUyYwLI=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs96d4VrvjfLxvuSP3cLVT87tXlD8pIaaW7WLX9mv vMx1v/W3FHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBEJqgyMmx/LLzCanKTqnWQ QIReLffBpYG/TVrZtlry33zqrXm9bBrDf6dPfy/+1zggt1ls09usTdH3ZnC6a3l7LSq45vxQq2L jNQ4A X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Stat-Signature: z36wiojdw9dpz8kje7htkggweehnxsmw X-Spam-Status: No, score=-18.8 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: 4ACAF1C0004 X-Rspam-User: X-HE-Tag: 1793440194-112561 X-HE-Meta: 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 rTKNvYOb j/xRsUMKIBOdYHoqkxBYh407kmuFUNeQbVoXDioAK+6q65VCSwWZdXgltHNPfZjvliNKucYqIJMFaGsZs+jmPz2nBDzTtRP445Lxr9NpiV3hMbtEcsQKSF+cWZ/X4EQy+RK9rNc4VOy3YoFiZdKDbQ1egGLWD8Agt54l7Ja84dxiDRrN2ej9Xe2RWO8JL4MJL0bwfrGpTJlPVLBDA5TFIQ1k5mjUVHiHKW9dk3+jXsBSVNoHWr4ppoHlNcjNOzAZBVOiD6z/r3lBgO2tHBjTDd/6kB0q6csEwDbCZNaBg/fCsSgJ8kmB/hYmDDgSU7XcbH8mg2ntlzxV2yCcZdie5KY0ES7g1lAPwROlZA3rGGGEkcxjAmtsIuzc+yoTq7l+9Nj7Lctyg4Nfd83hMaLmFt0hvB12YiHB1SINr4HkGAgiWcA0= 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 ] Tested-by: Muhammad Usama Anjum 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 732b8f926de6a..77d4bbf444bc2 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