From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793204405; b=SrsgKNGl0zIvn2ycd2+Wu6DJ49twRuKODFUfP4AywjD1KTKX2ZETa+iAhcXomnimtZE3 WrgQEF0QgzOsyJUw3Edpg+UKGbMz5hh8ihK9oWvLVwVyNgbTpmXoEnErFXSqbvN64rwh9 /SyZjta7qA3MDpJynFocQHtMxHdUf5BAnwAywoCR0E9UtceB8m1vfO/xePo3bIaXrMKMS /YEw1tvBVi2C80p2s0ldOdfHepEV/8nTGFuTEBI+BqQwEMyEzADkL4Al6RPmrrzEAVgca U3ksi3nq6gdu0HphXXGK78lShMPjTWKtlR4TWSqHOWou2mJQfvssgv12rBJjQWKqY6Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793204405; h=Received:DKIM-Signature:Received:Received:X-ME-Sender:X-ME-Received: X-ME-Proxy-Cause:X-ME-Proxy:Feedback-ID:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=0rATnQQTJ72YrBkABg0cEBhwiSsSBn8AUhfECRfpTKo=; b=rGHC33EEN81JYAuzG46D1qRG1yqJSVFXfn0iLL6BtfYQboeyVFaE987G5v05s4SVA7fD me6/mYv6uLKLVXU/o9RMPHmtZhbwltckJ8F39jIAM4AFSAi0rS7A2zLERYX+g77uWtuE9 haK3HaLHW+VcjJo5GOrg3SyX+XvvfhoizyZDDi2bEsL44+GQOfwlQ+PtJdR3FA5GFAY1b cNxQS5olosQ/t/JatTypu0XB+Oqu8rHD/QSuJCa2KHNJUwNRPnOH+D2zfwxZQ9i0f8am/ hKRx7g+tkUfeojfqH0QGxPno9VIILiRqPv2UTT/VVTrM62mbzN4r8tHqctbv7jEFIlw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=UmIij8vf; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42CF6606A31A for ; Wed, 28 Oct 2026 16:20:05 +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=UmIij8vf Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5B331F01829; Wed, 28 Oct 2026 16:20:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793204404; bh=0rATnQQTJ72YrBkABg0cEBhwiSsSBn8AUhfECRfpTKo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=UmIij8vf/k3vPosCEVWZkUrZaT3cJyYVso0ngmgXQnm5Qiwz68buSNqZW+8lvZjoD n0YcsWASKMCCTBNuGeBXY/Ms3PtYzYwRYf8VoSJsPvldppqlXhm/ReMYKNp5aGYec+ bRclZ/KKr85Vrl5c51fPSWiOVHybCrwKvtZUZkWO3SoYa65gKjFRgaBD3HYmic0a2D jyyACS3zLnDO6fxb9jvrrMGvWuy8xfS0UlWBNV+dLQPPZ7Ae1v0LSrWreUyqvGpnhf jOP40mj59weocaFNQoE6WmukOXdcYHTk9wH9w2g+LWyvb35SMyhiljJXypUkaQhRQG pptZToRJ0mYxw== Received: from phl-compute-02.internal (phl-compute-02.internal [10.202.2.42]) by mailfauth.ams.internal (Postfix) with ESMTP id 29073198005A; Wed, 28 Oct 2026 12:19:49 -0400 (EDT) Received: from phl-frontend-03 ([10.202.2.162]) by phl-compute-02.internal (MEProxy); Wed, 28 Oct 2026 12:19:59 -0400 X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: dmFkZTGclD1JbppB9HJ+wc+PBYUc7y+dixlkOiA2HsCm5bBLjgZcXtU5z4GDtO5noWzmDd ORQFP5u9B2gtbQIzAfn62HyoZPZzOaRlPLXMJbRuOKsJfFDAVc93Ms6EaNrHWEq6z6wsvt Vwv7YGYHYp1DmH0JFFFqpqagIBWKJjdY8K+9fHquSKFVK4QpWZo3/X+8b1lo1wJj7cOP/0 UxPerUKzYQfYIPe0+zZpOe+dudiR/ZmyEvfhO+buEi+HLpafl9BeNw9D79/rT5MOLUUGeC H20VI38/59YkMmPnP0Lyu8v9OMGay2+0LMnea7uAS3uuq0rtJ908MMUpIuTf0GbHo8UsAY ua+t7Qev6BT8kMHCeyM4V1m6u5YQwDA4moRebSE73U9F3vqd/sLjELfF2vONZb+ZcW5TQB 94GQy7Qy9EYuo6vu61hPJ1VjyjuMJ99xhWVMI+3gZz6H3VQ84mHv5w8TE9tnJChUhoUUP9 4BpLr6gQs04DR36/rOYGy/+LZjcGIu/GNpIN099cOSZ+EN2zqtR43z7EhAL94X1B/ytyyp oo/rRFI886c55KcN4on3qj6HWPCrIJtfc0D4lmBumEi5I8lrnU3HxQLS8Z22AYR9GbRHTz 75P/PVpblWhTAf4127jPQ1kO6sZzgqCljd55hkW2aMHmD3LDpX4z8/2t8a7Q X-ME-Proxy: Feedback-ID: i10464835:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 28 Oct 2026 12:19:46 -0400 (EDT) Date: Wed, 28 Oct 2026 16:19:45 +0000 From: Kiryl Shutsemau To: "David Hildenbrand (Arm)" Cc: 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 , 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 , 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 Subject: Re: [PATCH 02/46] fork: take mmap_lock before copying mm_struct Message-ID: References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-2-6f74bec9a5bb@kernel.org> X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261027-fixes_core-v1-2-6f74bec9a5bb@kernel.org> On Tue, Oct 27, 2026 at 12:17:22AM +0100, David Hildenbrand (Arm) wrote: > dup_mm() copies the parent's mm_struct before dup_mmap() takes the > mmap_lock. A concurrent brk() can leave the child with a stale mm->brk > and newer heap mappings, causing later brk() requests to fail. > > Other operations (e.g., PR_SET_MM) on the parent's mm_struct can similarly > cause inconsistencies. > > As a simple and robust fix, grab the parent's mmap_lock earlier. This > way we don't need to update individual mm fields in dup_mmap() and > keep missing ones. Stop updating the 4 existing members (total_vm, data_vm, > exec_vm, stack_vm), as that is now no longer required. > > Keep releasing the parent's mmap_lock in dup_mmap(), before > userfaultfd completion, to avoid moving the userfaultfd handling into the > caller. This should get cleaned up later. > > Move uprobe_start_dup_mmap() to preserve the lock ordering. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Reported-by: Josef Bacik > Reviewed-by: Lorenzo Stoakes (ARM) > Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov