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 87E31606A31B for ; Thu, 5 Nov 2026 21:31:09 +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=HthU2TK7; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ZFkFtso3 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=bT7cdtBA3g4ZjNdxCADmBOubkwzRkbH+TQ0hoqO6tiY=; b=HthU2TK7suDXErz2OI9F1zvhPd HIxxqS3szPXqTWV/O1hvCiTZ1gB5zJCtFIXavdMW8IDNs+YPOYsoS7LEikKBPah9y0bpCgCK1VTgq amMI32XHhrNWNsLVVxFdcT4h6nMuyJiBwwMdWkr7jvoGNFGb6hWVQ7PlfeOF+3xBMsGoM1PfW3x5x 9jkk3hwj46561wnYSsqRUWyQvaUndBzWK1mkOvQ19tdixDxZtu+96gIZwuz9t3dBxGoECHvOQYDrk oIeohToCYCLh6+WxjqimnJwwnLB19zXPlzlsEH13DicRPqsmIXWT16t6tC2F8YSm6URhPPh9LAh37 K/AOG4aA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xP3Bj-0000000ALTK-0Fmr; Thu, 05 Nov 2026 19:31:55 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xP39w-0000000AKhM-0KcN for kexec@lists.infradead.org; Thu, 05 Nov 2026 19:30:04 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 86072601C5; Thu, 5 Nov 2026 19:30:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 551AC1F00A17; Thu, 5 Nov 2026 19:30:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793907003; bh=bT7cdtBA3g4ZjNdxCADmBOubkwzRkbH+TQ0hoqO6tiY=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=ZFkFtso3C96AnTUnqfat70nSvPWig/+mlWw5M0UhnuCp5QJxgxNGQrORhQlrQkJ/y hC3IYuBkO3IUK23KYNgrztoNyDYmU4MR+D9gL2C8VjvK7vkMSvevOunoGmfWD0JNml vsF9OIiPC1HM3aRMk6Mbu6p74Dq5+9CvuKroZEovRvm/WILib1QicWaO1x2FWXQ/Gh 4URR7CizufYYPnmywgHmy0LbSoLzZeP9pgnBeUiBSkH3rjb0o92yRGCn9Np6O+kLCX Go0H2HcVBVV+M9zicMMj4k9ffVIUnGBdI26ePeddA9J3Se+pxAShijM1YnU9ctvKg+ O8G91Qj2o2VRQ== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RESEND v2 36/51] 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: <20261104-work-procfs-bugfixes-v2-36-021c84d852e0@kernel.org> References: <20261104-work-procfs-bugfixes-v2-0-021c84d852e0@kernel.org> <20261104-work-procfs-bugfixes-v2-36-021c84d852e0@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 19:30:00 +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/20261104-work-procf= s-bugfixes-v2-0-021c84d852e0@kernel.org?part=3D36