Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752392AbXBHSSS (ORCPT ); Thu, 8 Feb 2007 13:18:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752393AbXBHSSS (ORCPT ); Thu, 8 Feb 2007 13:18:18 -0500 Received: from mummy.ncsc.mil ([144.51.88.129]:50399 "EHLO jazzhorn.ncsc.mil" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752373AbXBHSSR (ORCPT ); Thu, 8 Feb 2007 13:18:17 -0500 Subject: Re: [PATCH 2/2] sysctl: Restore the selinux path based label lookup for sysctls. From: Stephen Smalley To: "Eric W. Biederman" Cc: Andrew Morton , Ingo Molnar , tglx@linutronix.de, linux-kernel@vger.kernel.org, selinux@tycho.nsa.gov, James Morris , Eric Paris In-Reply-To: References: <200701280106.l0S16CG3019873@shell0.pdx.osdl.net> <20070127172410.2b041952.akpm@osdl.org> <1169972718.17469.164.camel@localhost.localdomain> <20070128003549.2ca38dc8.akpm@osdl.org> <20070128093358.GA2071@elte.hu> <20070128095712.GA6485@elte.hu> <20070128100627.GA8416@elte.hu> <20070128104548.a835d859.akpm@osdl.org> <1170075866.8720.15.camel@moss-spartans.epoch.ncsc.mil> <1170872654.11912.87.camel@moss-spartans.epoch.ncsc.mil> <1170882738.11912.144.camel@moss-spartans.epoch.ncsc.mil> <1170946871.11912.250.camel@moss-spartans.epoch.ncsc.mil> Content-Type: text/plain Organization: National Security Agency Date: Thu, 08 Feb 2007 13:13:24 -0500 Message-Id: <1170958404.11912.313.camel@moss-spartans.epoch.ncsc.mil> Mime-Version: 1.0 X-Mailer: Evolution 2.8.2.1 (2.8.2.1-3.fc6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2584 Lines: 58 On Thu, 2007-02-08 at 10:53 -0700, Eric W. Biederman wrote: > Stephen Smalley writes: > > > > > Hmmm...turns out to not be quite enough, as the /proc/sys inodes aren't > > truly private to the fs, so we can run into them in a variety of > > security hooks beyond just the inode hooks, such as > > security_file_permission (when reading and writing them via the vfs > > helpers), security_sb_mount (when mounting other filesystems on > > directories in proc like binfmt_misc), and deeper within the security > > module itself (as in flush_unauthorized_files upon inheritance across > > execve). So I think we have to add an IS_PRIVATE() guard within > > SELinux, as below. Note however that the use of the private flag here > > could be confusing, as these inodes are _not_ private to the fs, are > > exposed to userspace, and security modules must implement the sysctl > > hook to get any access control over them. > > Agreed, the naming is confusing, and using private here doesn't quite > feel right. > > A practical question is: Will we ever encounter these inodes > in the inode_init() path from superblock_init? Possibly, during setup upon initial policy load (initiated by /sbin/init these days) from selinux_complete_init, as early userspace may have already been accessing them. > If all of the accesses > that we care about go through inode_doinit_with_dentry we can just > walk the dcache to get the names, and that should work for the normal > proc case as well. Walking the proc_dir_entry tree (or the ctl_table tree) is preferable as it is a stable, user-immutable representation. Also avoids taking the dcache lock. > A somewhat related question: How do you handle security labels for > sysfs? No fine grained security yet. Right, they are all mapped to a single label presently. I was thinking of handling that from userspace after introducing a setxattr handler for sysfs and a way to preserve the SID on the entry (likely caching it in the sysfs_dirent and propagating that to the inode when the inode is populated from the sysfs_dirent). Then early userspace could walk sysfs and apply finer-grained labeling from a configuration. > If it doesn't look easy to solve this another way I will certainly > go with marking the inodes private. -- Stephen Smalley National Security Agency - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/