Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752393AbbEGW7Y (ORCPT ); Thu, 7 May 2015 18:59:24 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45878 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751739AbbEGW7V (ORCPT ); Thu, 7 May 2015 18:59:21 -0400 Date: Thu, 7 May 2015 15:59:19 -0700 From: Andrew Morton To: Josh Triplett Cc: Linus Torvalds , Fengguang Wu , Iulia Manda , "Paul E. McKenney" , Fabian Frederick , Linux Memory Management List , linux-kernel@vger.kernel.org Subject: Re: [PATCH] devpts: If initialization failed, don't crash when opening /dev/ptmx Message-Id: <20150507155919.16ab7177e4956d8f47803750@linux-foundation.org> In-Reply-To: <20150507003547.GA6862@jtriplet-mobl1> References: <20150507003547.GA6862@jtriplet-mobl1> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1561 Lines: 41 On Wed, 6 May 2015 17:35:47 -0700 Josh Triplett wrote: > If devpts failed to initialize, it would store an ERR_PTR in the global > devpts_mnt. A subsequent open of /dev/ptmx would call devpts_new_index, > which would dereference devpts_mnt and crash. > > Avoid storing invalid values in devpts_mnt; leave it NULL instead. > Make both devpts_new_index and devpts_pty_new fail gracefully with > ENODEV in that case, which then becomes the return value to the > userspace open call on /dev/ptmx. It looks like the system is pretty crippled if init_devptr_fs() fails. Can the user actually get access to consoles and do useful things in this situation? Maybe it would be better to just give up and panic? > @@ -676,12 +689,15 @@ static int __init init_devpts_fs(void) > struct ctl_table_header *table; > > if (!err) { > + static struct vfsmount *mnt; static is weird. I assume this was a braino? > table = register_sysctl_table(pty_root_table); > - devpts_mnt = kern_mount(&devpts_fs_type); > - if (IS_ERR(devpts_mnt)) { > - err = PTR_ERR(devpts_mnt); > + mnt = kern_mount(&devpts_fs_type); > + if (IS_ERR(mnt)) { > + err = PTR_ERR(mnt); > unregister_filesystem(&devpts_fs_type); > unregister_sysctl_table(table); > + } else { > + devpts_mnt = mnt; > } -- 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/