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 1E214606A326 for ; Mon, 26 Oct 2026 23:25:10 +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=XmfZUdKj Received: by kanga.kvack.org (Postfix) id 31D666B05D9; Mon, 26 Oct 2026 19:25:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2F5166B05DA; Mon, 26 Oct 2026 19:25:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 20B196B05DB; Mon, 26 Oct 2026 19:25:09 -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 0129C6B05D9 for ; Mon, 26 Oct 2026 19:25:08 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 18D1114083C for ; Mon, 26 Oct 2026 23:25:08 +0000 (UTC) X-FDA: 85366360296.04.38A943B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf19.hostedemail.com (Postfix) with ESMTP id 4B45A1A0008 for ; Mon, 26 Oct 2026 23:25:06 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XmfZUdKj; spf=pass (imf19.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=1793057106; b=ElWL+hX+d0x3YQOk/ZQ44xuCuKE4+Y1y7a2oOrZXD8GBgGqDxLoex0EPW8ExbMCF4AOyK2 T+VN2Z3oNDXk6bZKDaOfNc2ZYQGSa9dsosOV6gVLs84LRG88zy+2X+fZLly2L6GM1jEa58 RjTS88n3FXlVdGEbjVTExtRGwkjjwlM= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=XmfZUdKj; spf=pass (imf19.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=1793057106; 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=NWNJ/XENAKSS8XJu2StXXvDx4pA/ZlIpefLloruQ3+A=; b=InXyDoKxDemUPv7ldOAysEt7wGkbbv5qqqmCY/zNVPCFzbeLucsgyk+TLiizxsSEsrqfLe v5xwCq+PUTo52yzxy8ZlilJyfE/NTgbnkPhZvtzGFWB5kflheIoGo4zz+lX6cbmTG0Hgz9 mhsmq2KZ3pgzzC3H0VTUZiK8+gY+mPE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 90FCA43A59; Mon, 26 Oct 2026 23:25:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BAC9B1F01825; Mon, 26 Oct 2026 23:24:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793057105; bh=NWNJ/XENAKSS8XJu2StXXvDx4pA/ZlIpefLloruQ3+A=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=XmfZUdKj2CDA3hO/9OSbirdo/tI8K3m4+KVIN68gYUkWYDqjcQkm5g1INwhB61XHz B7RwKeG1CHsN5S6OJkvQsHmA0cql1QWmgbZ5b07svv40y4SxyrPzL9VUHMao1+/lbv pDTINIXQaAyXCwuj/k/OuayFvhOlGgVfUtolZmXavmCRIrRKJuvsa8MOnJFaFRq87R SIHKlLe+V7Ng+b4lAvM+DKz0SlqtEc9SiBdUFWJwiu2lctCWh0cYkKTc28rEazIUI+ jxN1CCeJj3IYrRDtRR5yXE9lyp4+zAuIjWbwmIF85IHU5AghTyKrUsQAlewE4xpgIz p8s5ToS7ru13A== From: "David Hildenbrand (Arm)" Date: Tue, 27 Oct 2026 00:17:43 +0100 Subject: [PATCH 23/46] 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: <20261027-fixes_core-v1-23-6f74bec9a5bb@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, stable@vger.kernel.org, Josef Bacik , "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1288; i=david@kernel.org; h=from:subject:message-id; bh=SZZ0c1Ekk71/HNTctZ9IxQIrBH8id6NjD8hfDnFWvMg=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLu35/m/ShOQ+gHDwePwf/j9sIbLn+O83as/W7OorTuo pR2iufujlIWBjEOBlkxRZag4PsGL1+uq61242OGmcPKBDKEgYtTACbyTpyR4dflzBz7RJm7Wi7e fkozPU4pZU8RvNeV+djcwsszqL8ghuF/+r1nL/aekqm5sah+zstDGa/fJO6drqF1452p++uS9GA 1fgA= X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A X-Stat-Signature: gx4j47ekxs9gzh6ikj7gx6puqep6t513 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: 4B45A1A0008 X-Rspam-User: X-HE-Tag: 1793057106-625761 X-HE-Meta: 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 3bA4GaEI 4SOwnmJXKSerbuXBTzDewHwsz4DiuFMDLSsr1wiWuneo4lhy36DyX/ThrJ+may/1thumN71QMZ2BJ/XZ3+JcilQw0YKZ2McMqbtyR6VTaY2UuBrpyoAt2Obqz1Xxjaqms88MKPvjdXXSSXp2Uj5lFLZU5GCfl/hAKfOM1Px1b4p6T+cwhxqhhM1y926vvz3BE6kxOBX6PP4X35s4yY4NlRrkoT/GSeWaenFVW1uxC7gE0lb7PvzaJAMTrn7h9ikbZLhtamskVXgEyq2w01SxZiD1wZVuiv6+0VSAtmn0vBxK09MeRZklCLjCbB4BknZlub1Qzcr2wOrKyr7+GOFwG6tMHDOkTRjHFs7X5FBnag3TZwnn4ar7+ImweNPP34hmWlYSu 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 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 669f71d485d02..7e30b5ff17be1 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