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 DA746606A324 for ; Sat, 31 Oct 2026 09:46:17 +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=d6CFfneP Received: by kanga.kvack.org (Postfix) id E7EF86B05D8; Sat, 31 Oct 2026 05:46:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E2F056B05D9; Sat, 31 Oct 2026 05:46:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D1EB06B05DA; Sat, 31 Oct 2026 05:46:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 999536B05D8 for ; Sat, 31 Oct 2026 05:46:16 -0400 (EDT) Received: from smtpin09.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 2928F1A04EC for ; Sat, 31 Oct 2026 09:46:16 +0000 (UTC) X-FDA: 85382440752.09.8C2FD34 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf20.hostedemail.com (Postfix) with ESMTP id 63EE41C0009 for ; Sat, 31 Oct 2026 09:46:14 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=d6CFfneP; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1793439974; 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=4sgsef0PgIF0cfrADdJuNAAJq268avrj1EIWVyDlN9A=; b=sHIRxMuxytevUetL92IcaHYxzcsqiwgdeAKQdD5FcRVQUrCeq7gFJtPb3UcANTLcNlWWlM 2OrU2Cb+K52Nb+12mcvQDeY3jMA6a2S4BIizasNKaE5PJw7KoHVHG33ZxnkkYCw0I5wAJf /XFs11TcM8I3uTwmD0q1x77pW48gybM= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=d6CFfneP; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793439974; b=mHbuyZd/2vPwt7e9JZvqwGmqkB3N9gAGquGAz9XsLVsh8KeNaJyUudXl2VXQ1oRtFeHK+5 JUoXBF3luK1xortLG7m4NF40mXcbjZbWi6I48oZ/hlEulILa95gtXl/7Rb6fGMIcnWhXjG aI5cmHJ+/wVxZqHLbZ1IG6nJkuYvpQc= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id B17AA41464; Sat, 31 Oct 2026 09:46:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6136E1F000C1; Sat, 31 Oct 2026 09:45:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793439973; bh=4sgsef0PgIF0cfrADdJuNAAJq268avrj1EIWVyDlN9A=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=d6CFfnePukIWxq1RflVVt4wxWBc+6vCaK03YtXkPiVGAT1MLhmGttqbCKpZC8CMv0 ykZG9YuZhqJBGj8aR09OSLgRuWTYMZWKwLUnOtAFD0NmRWhh/hkNYdyjvdkGrtM/HC NvXMCLg235yYjJ1P9mJHTNNH7LQX4WGY6VQxjXRLERdE7L37vvhfQideQle/aO4CF2 rz9IJxRxQ+TD0DOdP47cmawMrJuPX8KczA2npuhKSEktnAwI/DZutaxbl1koK56PVe 4Qx6oqX4wL1+I/FemH+A6y6sdwfYTdtWxi7NEEoGuMBtRUXETKv8bzi+XlHEkQntS7 4jzXemYA3bcMA== From: "David Hildenbrand (Arm)" Date: Sat, 31 Oct 2026 10:39:52 +0100 Subject: [PATCH v3 23/47] mm/userfaultfd: write-lock the VMA before waking waiters when unregistering X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261031-fixes_core-v3-23-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, stable@vger.kernel.org, Josef Bacik , Muhammad Usama Anjum , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1507; i=david@kernel.org; h=from:subject:message-id; bh=wm0iwUtDDosDLjqj9xBcxV65LFmKykeK8WHMHyZPLHw=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLKebs+QOvwkeiXTRJbcv69PJk23spi0JO3lV54Jugxc1 +3fPj4R2VHKwiDGwSArpsgSFHzf4OXLdbXVbnzMMHNYmUCGMHBxCsBEXhkw/K8Jnfd9x5bTzUxX pftZNxgezJ8YN90hhLtU3enYreUr/mQwMlwUz5Tcc+IGq0Txmea3//4c6PzmP2uueYjKLiaP75X zrrMAAA== X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Rspamd-Queue-Id: 63EE41C0009 X-Rspam-User: X-Stat-Signature: gru5j88gmqtxaab8f77qjqhhojgszkc5 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: rspam03 X-HE-Tag: 1793439974-41362 X-HE-Meta: U2FsdGVkX1+XWP/udkuu9BckPZN9H/CaN/V+yKKg0mV9vLQnwoITBW3UdQnZ+Bw/BbNtWgKSfAQ6u1uduiI1+x1ISXFc7XkktUmXsndCnxGA7uCvFwOy9GMS6Wgx7zGjNjw79r/6ytizEqYPKXhPD5YLJRkqt3uJ3bFFEHAD+mTRtlGvfNgLPzc3/Fi/GfKDzWKwf+69GtsyYFdnTPkk+PjfKaS6u1W1wVB09E0OifKQvrXnCakTSEOS3q7Xavqp0Ay9mK/62CkYHNIfdZKPoIDHBoQts9+qYh1EKmtDCHtG7wGtwM/33yByLBN7W5C9ZedS+aZAPEVLAqrAczUjQdwMyb7qgxCA6FaLqeBOfQuLcoS9/tolfYgs8LWrnye0pJtD7PlB/16UrsKyLFAOmTL+PWdgqi31MI1q9wz22PPq6M6m3Oge9gP2kFygsYHKnxBxWa0a+u27Ux00dt2jnAlaZTJSLyZS/WFgPhuPOTPJ+/4CVqe36roGK1ExyTeqlXqwxP8807pVRh2ZGMrPUICP1BfNXosu6XwKWFWmrDloFKDKa/cHmAuy3Nx2xOW7qxkj1hHzhW1FRF1vCuxrX2oV7M8/agfHNbn6iCj9FdcJP+cOx4NJ5iTbn7CAMOKSmgyze9rO1p+6J5hrYJjT1dLMFVqqnr3S4GumECB++rumB7KQx5ukSaIu/qozl4b4FVIQeiS9mlF8ux4fX1gPIfXOPFWbnu7PxW/B9rR7+4Rwk5+qnxu6W8ajBB0Dt7bZxeXLC87szHJcttdxASXBkU+1vDQnFql2M8q4dF5W8z6uw3cYgaJlK4OPkl3FW/DVyYYdVdT/jG/niOuVnNweF/C6VB6IsCTEXSqq9EYyjXSeIcAq0xY8WJSn4qxprjqBngroMbOzHdGfdydKylrronqVqfH32haaSsAXTzDH/bm2dmrgd2JZ5DUujfrSNnm5C32rfbF7KL3VubJVDPY ZWQa8sHd NDBuoGAE8tYjQVdZpI5+l939aJmE9vcBaemDcbZaabeQll9xBqn8jBYe0aFBVA++bSd5UctHQgZ3ZH+/w2Stssw7Rb+bE6/U3qGXSe8mHNsxhzcouT9nrnNKdGmJarLmDQXmKs0ZdoaS08ao0RaIJUi6gBNnUdtWhoslaBtkBkGDeu8Q7XZG6xl19ihGsU+HgsbmT2d7HlMw9bbkFI3XTz8MQivQHs73I6sxxw7p4gByprwcPonHTV9CNEyya5jc9AnOh7BElz26OnQ1XniLmOIKWrzIDolh+zkpijwp4GG/xr65vjr51wdd2wrAem/+JI/r6DFT1Zc9h/NsIN1g7HI6FfYwfodRDwBmyxYCLnMM/664sX5g0FzIyT8wfuRAJYa4jUJEOK6VOnWAFxd1tELPZqD0uOSRir0luUtq2lohH6Yx7Fo6Fi8L4YqqEIX2EWcWe9sdLpSTpozg= 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 userfaultfd_unregister() wakes pending missing faults before clearing the VMA's userfaultfd registration. With per-VMA fault locking, holding mmap_lock for write does not prevent another fault from queuing after the wakeup but before userfaultfd_clear_vma() write-locks the VMA. That waiter can then remain asleep indefinitely. Call vma_start_write() before waking waiters. Existing fault handlers queue themselves before dropping the VMA read lock, and new readers are excluded until mmap_write_unlock(). Fixes: 29a22b9e08d7 ("mm: handle userfaults under VMA lock") Cc: stable@vger.kernel.org Reported-by: Josef Bacik Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Suren Baghdasaryan Tested-by: Muhammad Usama Anjum Signed-off-by: David Hildenbrand (Arm) --- mm/userfaultfd.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 928ad95eeb2ba..3ca04b582329f 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -3991,6 +3991,9 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, start = vma->vm_start; vma_end = min(end, vma->vm_end); + /* Prevent new userfaults from being queued after the wakeup. */ + vma_start_write(vma); + if (userfaultfd_missing(vma)) { /* * Wake any concurrent pending userfault while -- 2.43.0