From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 584E86071C0B for ; Tue, 3 Nov 2026 14:48:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=ykxDVH/+; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=KyP0Q9eL DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Reply-To:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Date: Content-Transfer-Encoding:Content-Type:References:In-Reply-To:Cc:To:Subject: From:Message-ID:MIME-Version:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Unsubscribe-Post:List-Owner; bh=UPzqk7+6Hl7aBBk0FqNi8TIlMxqX8AAV9w+mELiQtKI=; b=ykxDVH/+89wTf1hKTOw5XJ75et lhhXm0IlvjzXtgXBtk6hbjcO95HT84cnkRiNbUVsl999/Ug7SIzQy+aFnYGI1ksOGjykAYINKprQu sbGYJKRWmN+/HUqOpj7S68sCnOXcIO3zF3H8eAVl4wwiUKEb6uitjr8sQ9AXmy6zXW8TkiqIrlLEI 2X3WtblK1SpXOfojg4Do7y+cLd5jvIsMbTUQDC/IY6N4/574bkohUkINVGSY0IsaH72TO7bt/FUnv mJyONw1Ry+MeCSa8ESirr+OFxUCEjPj+Ek1iCswtxBY4OmtXXFqLWYfLjWeDvsuNqDYqP4sRkBVQz zc4YLYOw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xOFo8-00000002lLt-3wf8; Tue, 03 Nov 2026 14:48:16 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xOFo7-00000002lIA-0qJV for kexec@lists.infradead.org; Tue, 03 Nov 2026 14:48:15 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C5C3941874; Tue, 3 Nov 2026 14:48:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E8171F00A15; Tue, 3 Nov 2026 14:48:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793717294; bh=UPzqk7+6Hl7aBBk0FqNi8TIlMxqX8AAV9w+mELiQtKI=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=KyP0Q9eL1hFy4s0NX1iEANFqNWyeYeRsq7ov2+9cVKjWEzToC131fOzh5r7yFlHar pIVojox+9qRsPY8VX6mwReyYX3yM4SFOa3iFCUR8BcHSlpdr+HkALlcvSK2dwXQvk+ HMq+2JewLsNDNoadtorpcqyv8VmsXaU+6ywYj9q8fu0Af5xcC0FEy2hjbC8xdQfcsf dvZi4J3QGSXjFPKV0tBhEW3a5ygQMYHiaBbiGSmEoo2Asd7E0ogclqFTlRO95k9T0A bUc528cBptya5ifedq5lG00IS5w0DzqO8jOfnUVY117pj0lbTuRQLJGRAkw4BQaw/M y5RlNwpIYj6xg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RFC 23/38] proc: don't let NOMMU map procfs files To: "Christian Brauner" Cc: "Linus Torvalds" , "Jann Horn" , "Josef Bacik" , "Chris Mason" , "Jeff Layton" , NeilBrown , "Eric Dumazet" , "Thomas Gleixner" , "Al Viro" , "Jonathan Corbet" , "Christoph Hellwig" , "Greg Kroah-Hartman" , "Joel Granados" , "Kees Cook" , "Jan Kara" , "Jan Kara" , linux-s390@vger.kernel.org, coreteam@netfilter.org, kexec@lists.infradead.org, linux-pci@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-usb@vger.kernel.org, samba-technical@lists.samba.org, linux-m68k@lists.linux-m68k.org, linux-serial@vger.kernel.org, "Takashi Iwai" , linux-ext4@vger.kernel.org, "Chuck Lever" , tytso@mit.edu, "Heiko Carstens" , "Vasily Gorbik" , "Alexander Gordeev" , "Christian Borntraeger" In-Reply-To: <20261102-work-procfs-bugfixes-v1-23-59422ed3e465@kernel.org> References: <20261102-work-procfs-bugfixes-v1-0-59422ed3e465@kernel.org> <20261102-work-procfs-bugfixes-v1-23-59422ed3e465@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 03 Nov 2026 14:48:11 +0000 X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "kexec" X-Spam-Status: No, score=-10.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: > Every procfs file has a ->mmap since commit 786d7e1612f0 ("Fix > rmmod/read/write races in /proc entries"), whether the entry has a > ->proc_mmap or not. On NOMMU validate_mmap_request() takes that to mean > the file can be mapped. procfs has no ->mmap_capabilities so a regular > file gets NOMMU_MAP_COPY, and a private mapping never calls ->mmap at > all. Instead do_mmap() takes nommu_region_sem for writing and > do_mmap_private() reads the file into the copy with kernel_read(). >=20 > Reading /proc/maps takes nommu_region_sem as well: >=20 > mmap(NULL, 4096, PROT_READ, MAP_PRIVATE, open("/proc/maps", O_RDONLY), = 0) >=20 > do_mmap() // down_write(&nommu_region_sem) > -> do_mmap_private() > -> kernel_read() > [ ... ] >=20 > Reported-by: Chris Mason > Fixes: 786d7e1612f0 ("Fix rmmod/read/write races in /proc entries") > Cc: stable@vger.kernel.org > Signed-off-by: Christian Brauner (Amutable) Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261102-work-procf= s-bugfixes-v1-0-59422ed3e465@kernel.org?part=3D23