From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH 4/7] Teach SELinux about a new userfaultfd class Date: Sat, 12 Oct 2019 17:46:16 -0700 Message-ID: References: <20191012191602.45649-1-dancol@google.com> <20191012191602.45649-5-dancol@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Daniel Colascione Cc: Andy Lutomirski , Linux API , LKML , Lokesh Gidra , Nick Kralevich , Nosh Minwalla , Tim Murray List-Id: linux-api@vger.kernel.org Archived-At: List-Archive: List-Post: On Sat, Oct 12, 2019 at 5:12 PM Daniel Colascione wrote: > > On Sat, Oct 12, 2019 at 4:09 PM Andy Lutomirski wrote: > > > > On Sat, Oct 12, 2019 at 12:16 PM Daniel Colascione wrote: > > > > > > Use the secure anonymous inode LSM hook we just added to let SELinux > > > policy place restrictions on userfaultfd use. The create operation > > > applies to processes creating new instances of these file objects; > > > transfer between processes is covered by restrictions on read, write, > > > and ioctl access already checked inside selinux_file_receive. > > > > This is great, and I suspect we'll want it for things like SGX, too. > > But the current design seems like it will make it essentially > > impossible for SELinux to reference an anon_inode class whose > > file_operations are in a module, and moving file_operations out of a > > module would be nasty. > > > > Could this instead be keyed off a new struct anon_inode_class, an > > enum, or even just a string? > > The new LSM hook already receives the string that callers pass to the > anon_inode APIs; modules can look at that instead of the fops if they > want. The reason to pass both the name and the fops through the hook > is to allow LSMs to match using fops comparison (which seems less > prone to breakage) when possible and rely on string matching when it > isn't. I suppose that whoever makes the first module that wants to use this mechanism can have the fun task of reworking it. There's nothing user-visible here that would make it hard to change in the future.