From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=172.105.4.254 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793907004; b=EUYbJzl0B59kVpo66MGQdg6Ekf3torqfIiW19ymmUcIKONdtnrld8aDRr1CXSAGee3mE 0ohntZEuUN0cApMG9Ufghj9FikmmIu2o5CJVlCPyfiJXmuhpDq2uNNVJEn0B0T5nnaaji Jyp2jEQZPppPGDFFi8Go+MvjJ7rAc3sHKWj0rPLUCLs0bCrAvG7/pWlG6UT4/hW5exEMz o4mj1VhDYXIzoz75w7u5RXkqBgWypp8Wjqw3lNiHNmH6CFX9as/cfdYbK6UWtALkFrxmL L/8uRO0KBjDci+m5wm0hc30PSA8/+hI/FMcCJuL9QaycYblNnFcKgPYzHzdPHqPvZjA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793907004; h=DMARC-Filter:Received:Received:DKIM-Signature:Message-ID:From: Subject:Reply-To:To:Cc:In-Reply-To:References:Content-Type: Content-Transfer-Encoding:Date; bh=bT7cdtBA3g4ZjNdxCADmBOubkwzRkbH+TQ0hoqO6tiY=; b=x+WJ+0mNDrU36E8331T558K1H57sDaUwLz7v2o5RQ5G5H//IjDUNDGmaISUHyz+MicpL dgOuBZrhXltA56fY6YCAlIoVEtSrsKDJorIUKu6bqmw0fzS0L1OkPxtg6QR8+Mc/JdBDs wNrpdixx067StAJQdmkZHm4zQA6TPVGcYd0+iKc3kRQra09mEm0Dn1d+WksgbsCM0BRNs JIB76jsCmNnpyBveSUhL6YR7f+K+3mjl7DTGQ3yD+a5Tt+mL347oz527OLyq1GkzysuBr x8/y1r7p4fOufgw7KKVd6Gxtu5gXyQHj+rvSJZ5qaYEdRzN0ziGZh02VUwLKQDDRt9A== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=kernel.org; spf=pass smtp.mailfrom=kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ZFkFtso3; arc=none smtp.remote-ip=172.105.4.254 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) (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 406E36082BDA for ; Thu, 5 Nov 2026 19:30:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 406E36082BDA Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.org 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=ZFkFtso3 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 Reply-To: sashiko-reviews@lists.linux.dev 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-Mailing-List: linux-m68k@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > 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