From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757924Ab2HWMe3 (ORCPT ); Thu, 23 Aug 2012 08:34:29 -0400 Received: from mail-lpp01m010-f46.google.com ([209.85.215.46]:56620 "EHLO mail-lpp01m010-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753390Ab2HWMe0 (ORCPT ); Thu, 23 Aug 2012 08:34:26 -0400 Date: Thu, 23 Aug 2012 16:34:22 +0400 From: Cyrill Gorcunov To: "J. Bruce Fields" Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Al Viro , Alexey Dobriyan , Andrew Morton , Pavel Emelyanov , James Bottomley , Matthew Helsley , aneesh.kumar@linux.vnet.ibm.com Subject: Re: [patch 4/9] fs, exportfs: Fix nil dereference if no s_export_op present Message-ID: <20120823123422.GB9112@moon> References: <20120823104323.040550004@openvz.org> <20120823104725.830795272@openvz.org> <20120823121230.GC29943@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120823121230.GC29943@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 23, 2012 at 08:12:30AM -0400, J. Bruce Fields wrote: > On Thu, Aug 23, 2012 at 02:43:27PM +0400, Cyrill Gorcunov wrote: > > If there is no s_export_op present in a target superblock > > we might have nil dereference. > > Is that NULL dereference possible with current code, or is it a check > you're adding to account for a new caller that you're about to add? > > I believe it's the latter, but this would be a good thing to make clear > in the changelog. With the current code it seems to be impossible (well, i can't be sure about nfs caller) because do_sys_name_to_handle does check for s_export_op to exist. Updated changelog below. After all I think not checking s_export_op was a mistake in general -- this routine is exported to other modules but has no a single line of comment about possibility of nil dereference. --- From: Cyrill Gorcunov Subject: fs, exportfs: Escape nil dereference if no s_export_op present This routine will be used to generate a file handle in fdinfo output for inotify subsystem, where if no s_export_op present the general export_encode_fh should be used. Thus add a test if s_export_op present inside exportfs_encode_fh itself. Signed-off-by: Cyrill Gorcunov CC: Pavel Emelyanov CC: Al Viro CC: Alexey Dobriyan CC: Andrew Morton CC: James Bottomley CC: "Aneesh Kumar K.V" CC: Alexey Dobriyan CC: Matthew Helsley CC: "J. Bruce Fields" CC: "Aneesh Kumar K.V" --- fs/exportfs/expfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-2.6.git/fs/exportfs/expfs.c =================================================================== --- linux-2.6.git.orig/fs/exportfs/expfs.c +++ linux-2.6.git/fs/exportfs/expfs.c @@ -357,7 +357,7 @@ int exportfs_encode_fh(struct dentry *de */ parent = p->d_inode; } - if (nop->encode_fh) + if (nop && nop->encode_fh) error = nop->encode_fh(inode, fid->raw, max_len, parent); else error = export_encode_fh(inode, fid, max_len, parent);