From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756623Ab0JWME2 (ORCPT ); Sat, 23 Oct 2010 08:04:28 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:52055 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754671Ab0JWME1 (ORCPT ); Sat, 23 Oct 2010 08:04:27 -0400 Date: Sat, 23 Oct 2010 13:04:26 +0100 From: Al Viro To: Jiri Slaby Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, "Dr. Werner Fink" , Alan Cox Subject: Re: [PATCH 28/49] tty: Add a new file /proc/tty/consoles Message-ID: <20101023120426.GN19804@ZenIV.linux.org.uk> References: <20101022175112.GC13489@kroah.com> <1287771688-14805-28-git-send-email-gregkh@suse.de> <4CC2C9A8.1040003@suse.cz> <20101023115129.GM19804@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101023115129.GM19804@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 23, 2010 at 12:51:29PM +0100, Al Viro wrote: > On Sat, Oct 23, 2010 at 01:40:24PM +0200, Jiri Slaby wrote: > > On 10/22/2010 08:21 PM, Greg Kroah-Hartman wrote: > > > +/* > > > + * Used for open /proc/tty/consoles. Before this detect > > > + * the device ID of file descriptor 0 of the current > > > + * reading task if a character device... > > > + */ > > > +static int tty_consoles_open(struct inode *inode, struct file *file) > > > +{ > > > + struct files_struct *curfiles; > > > + > > > + current_dev = 0; > > > + curfiles = get_files_struct(current); > > > + if (curfiles) { > > > + const struct file *curfp; > > > + spin_lock(&curfiles->file_lock); > > > + curfp = fcheck_files(curfiles, 0); > > > + if (curfp && curfp->private_data) { > > > + const struct inode *inode; > > > + dget(curfp->f_dentry); > > > + inode = curfp->f_dentry->d_inode; > > > + if (S_ISCHR(inode->i_mode)) { > > > + struct tty_struct *tty; > > > + tty = (struct tty_struct *)curfp->private_data; > > > + if (tty && tty->magic == TTY_MAGIC) { > > > > Ah, I've just understood what this code does. It seems, that the 'tty' > > at this point may be already freed (e.g. people don't set private_data > > to NULL). Please explain in the code why it can't... > > Please, don't. Even leaving aside the fact that it's mind-bogglingly > broken (->private_data can be _ANYTHING_, including arbitrary number cast > to pointer), you really shouldn't screw your way through the descriptor > table in the first place. > > Strongly NACKed. PS: "you" above applies to whoever had produced that patch, of course, not to Jiri. PPS: "device name of stdin of last process opening that file, if that stdin happened to be a tty" is an interesting thing to put into global variable. What does one do to it?