From: Marcelo Tosatti Subject: Re: [PATCH 2.4] SGI 932676 link_path_walk refcount problem allows umount of active filesystem Date: Fri, 25 Mar 2005 16:58:56 -0300 Message-ID: <20050325195856.GB15383@logos.cnet> References: <1111454677.1991.766.camel@hole.melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linux Kernel Mailing List , Linux NFS Mailing List , Linux AutoFS Mailing List To: Greg Banks In-Reply-To: <1111454677.1991.766.camel@hole.melbourne.sgi.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Tue, Mar 22, 2005 at 12:24:37PM +1100, Greg Banks wrote: > G'day, > > The attached patch fixes a bug in the VFS code which causes > "Busy inodes after unmount" and a subsequent oops. Applied, thanks. > > Greg. > -- > Greg Banks, R&D Software Engineer, SGI Australian Software Group. > I don't speak for SGI. > > Following an absolute symlink opens a window during which the > filesystem containing the symlink has an outstanding dentry count > and no outstanding vfsmount count. A umount() of the filesystem can > (incorrectly) proceed, resulting in the "Busy inodes after unmount" > message and an oops shortly thereafter. > > Systems using autofs-controlled NFS mounts are especially vulnerable, > as autofs both increases the number of unmounts happening and does NFS > mounting in response to lookups which can result in multiple-second > vulnerability windows. However the bug could happen on any filesystem. > > This patch adds a mntget()/mntput() pair around the link following code > (as the 2.6 code does). Attempts to umount() during link following > now return EBUSY. > > > Signed-off-by: Greg Banks