From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 9 Jan 2014 22:13:03 +0000 From: Al Viro To: Eric Paris Cc: Steven Rostedt , LKML , Stephen Smalley , James Morris , Paul Moore , Andrew Morton , "Paul E. McKenney" , stable Subject: Re: [PATCH] SELinux: Fix possible NULL pointer dereference in selinux_inode_permission() Message-ID: <20140109221303.GI10323@ZenIV.linux.org.uk> References: <20140109101932.0508dec7@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Jan 09, 2014 at 10:31:55AM -0500, Eric Paris wrote: > Didn't Al find this/something very similar. I really hate this > solution. Why should every LSM try to understand the intimate > lifetime rules of the parent subsystems? The real problem is that > inode_free_security() is being called while the inode is still in use. > While I agree with the assessment, I disagree with the solution. Let > me try to find where Al and Christoph talked about this.... Because LSM has stuck its fingers into the guts of those filesystems, obviously. Just RCU-delay freeing the damn thing and treat NULL ->i_security in ->permission() (which can happen only with MAY_NOT_BLOCK in mask) as "return -ECHILD and let the caller deal with that". Modifying every ->destroy_inode() is obviously wrong - there's a lot more filesystems than LSM buggers in the tree.