From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6B7D47ACD7 for ; Tue, 13 Oct 2026 03:31:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=18.9.28.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791862298; cv=none; b=c1K0pqq696OApKeHuEgNMmGHL2FCouJJQQ4wbpHXV9xRehtR9A9duKSUYByUNPCMzQDVYoQuEj0QhWu9isVKoXES9d5LgVZ1XEAaSn2UOOIGluzJ+m//QMEQhSGRWBZtWKazdl2bJxuf+hgjPcbfraDtuhoKllf+VkjAJHOEb2A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791862298; c=relaxed/simple; bh=cjyBjRJkApVsOaANK3jfZk+FCb9JFAhCOpaDsfDJ12s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dd080DBh+j8fsvrk2UnZEO/uNO8Sfez5AmDD9gK3cf6X/cHcqYR74GxzCG8emgFrgI9n/h39IKfGIR5VSnR/+EiQCjOMoM24i8kmk1sSTa43HlsqcB3aE8XUta/Fvj1ZMs6wsfMoQHb86DqiZjy7M9nL+eE1AMWMjTYyl9hnWIs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu; spf=pass smtp.mailfrom=mit.edu; dkim=pass (2048-bit key) header.d=mit.edu header.i=@mit.edu header.b=eWUN1mCY; arc=none smtp.client-ip=18.9.28.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=mit.edu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mit.edu Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mit.edu header.i=@mit.edu header.b="eWUN1mCY" Received: from macsyma.thunk.org (pool-173-48-111-204.bstnma.fios.verizon.net [173.48.111.204]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 69D3VPQV026428 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 12 Oct 2026 23:31:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing; t=1791862288; bh=d4H1hHVaQBRXson3FwMJdk9nzEsQQmVUiNyZKfJ6bNw=; h=Date:From:Subject:Message-ID:MIME-Version:Content-Type; b=eWUN1mCYULi7ZnKjU3d2UCy6E14hFO95ypvxx0FutOyDf2C9kXSYgW1Oq1YczokIz me8Ma8dWsMJ5NYEdT6h4p0RSMRrnj1ColeXRnHL5O1mDwkmfHg4z79AkC37H0b8XJz WUTnyxElFYDF0l2evtl6OqIR3VJq++KGTBceRWSzUBBxgl3ogy0vu7gakzL6C5YDwy WVnq75i/lviMtxQEgVaXNM3CODPKbncR/rMOolahFqhwpj6Q4KBXjf4WMAHlIn6TvT JyYLRS5j7KCGW5ksH/HJPV0sE8N99oKQ9ZYS9iiMmIuTiofxBawZY7phu6hzmLUdzs 6x/w6QuHMXnHw== Received: by macsyma.thunk.org (Postfix, from userid 15806) id B3BB320508A9; Mon, 12 Oct 2026 23:30:25 -0400 (EDT) Date: Mon, 12 Oct 2026 23:30:25 -0400 From: "Theodore Tso" To: Guanglei Zhu Cc: Jan Kara , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, guozh23@xiaopeng.com Subject: Re: [PATCH] ext4: check CAP_SYS_ADMIN in ext4_ioctl_get_tune_sb() Message-ID: References: <20261012060844.836001-1-zhugl3@xiaopeng.com> <20261013020145.1297074-1-zhugl3@xiaopeng.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261013020145.1297074-1-zhugl3@xiaopeng.com> On Tue, Oct 13, 2026 at 10:01:45AM -0500, Guanglei Zhu wrote: > > You are probably right that reading these parameters is not > sensitive on its own: most of them are already visible through > /proc/mounts or statfs(), and the superblock is readable by anyone > with read access to the block device. The argument of my patch was > the asymmetry with the SET side rather than an actual leak. > > I'm happy to drop this patch if Ted confirms that the missing check > was deliberate. Yes, it's deliberate, precisely because the parameters are visible in /proc/mounts and in /proc/fs/ext4//options. (The latter shows *all* of the mount parameters currently active, whereas the former show those mount options which differ from the defaults.) There should be nothing in the file system parameters which are secret; things like keying information for fscrypt are not passed in the mount options, for Very Good Reasons; instead we use the Linux Key Management facility[1]. As far as I'm concerned, storing passwords in the mount options ala cifs[2] is an anti-pattern. [1] https://man7.org/linux/man-pages/man7/keyrings.7.html [2] https://man7.org/linux/man-pages/man8/mount.cifs.8.html - Ted