From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joseph Salisbury Subject: Re: Race inotify_rm_watch vs umount Date: Tue, 06 Mar 2012 16:09:55 -0500 Message-ID: <4F567D23.9040309@canonical.com> References: <87r572nd9k.fsf@devron.myhome.or.jp> <1307713566.2577.20.camel@localhost.localdomain> <20110610143550.GZ11521@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: hirofumi@mail.parknet.co.jp, john@johnmccutchan.com, rlove@rlove.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: viro@zeniv.linux.org.uk, eparis@redhat.com Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 03/06/2012 04:02 PM, Joseph Salisbury wrote: > > > Forwarded conversation > Subject: *Race inotify_rm_watch vs umount* > ------------------------ > > From: *OGAWA Hirofumi* > > Date: Fri, Jun 10, 2011 at 7:20 AM > To: John McCutchan >, Robert Love >, Eric Paris > > Cc: linux-kernel@vger.kernel.org , > linux-fsdevel@vger.kernel.org > > > Hi, > > I'm looking the race inotify_rm_watch() vs umount(). This race become the > cause of Oops. You can see the oops at > > https://bugzilla.kernel.org/show_bug.cgi?id=22602 > > So, what race? > > umount inotify_rm_watch > ... fsnotify_destroy_mark() > fsnotify_destroy_inode_mark() > /* removed from > i_fsnotify_marks */ > generic_shutdown_super() > fsnotify_unmount_inodes() > put_super() > iput() > iput_final() > /* this is after > put_super() */ > > Like above, inotify doesn't guarantee to call final iput() before > put_super(). With this violation, FS driver can oops. > > Well, so, what are requested for inotify? We can't simply take > sb->s_umount in inotify_rm_watch()? > > Any ideas? > > Thanks. > -- > OGAWA Hirofumi > > -- > 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/ > > ---------- > From: *Eric Paris* > > Date: Fri, Jun 10, 2011 at 9:46 AM > To: OGAWA Hirofumi > > Cc: John McCutchan >, Robert Love >, linux-kernel@vger.kernel.org > , linux-fsdevel@vger.kernel.org > > > > Ok, I see what you are saying, I'll see what I can do. I'm a little > scared to call something like iput() under a lock though. I might be > able to make the bigest lock a mutex and fix this.... > > I'll add this to my test suite. > > -Eric > > > > umount inotify_rm_watch > > ... fsnotify_destroy_mark() > > fsnotify_destroy_inode_mark() > > /* removed from > i_fsnotify_marks */ > > generic_shutdown_super() > > fsnotify_unmount_inodes() > > put_super() > > iput() > > iput_final() > > /* this is after > put_super() */ > > > > Like above, inotify doesn't guarantee to call final iput() before > > put_super(). With this violation, FS driver can oops. > > > > Well, so, what are requested for inotify? We can't simply take > > sb->s_umount in inotify_rm_watch()? > > > > Any ideas? > > > > Thanks. > > > -- > > ---------- > From: *Al Viro* > > Date: Fri, Jun 10, 2011 at 10:35 AM > To: Eric Paris > > Cc: OGAWA Hirofumi >, John McCutchan > >, Robert Love > >, linux-kernel@vger.kernel.org > , linux-fsdevel@vger.kernel.org > > > > Which lock would that be? I don't see any good candidates in there... > > Hello, It appears this bug still exists in the 3.2 kernel[0]. There was some discussion about this bug in this thread and in the bug[1]. However, there haven't been any updates in a while. Has there been any further findings on this issue? Thanks, Joe [0] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/922906 [1] https://bugzilla.kernel.org/show_bug.cgi?id=22602