Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932523Ab2HWPWN (ORCPT ); Thu, 23 Aug 2012 11:22:13 -0400 Received: from fieldses.org ([174.143.236.118]:47810 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758860Ab2HWPWG (ORCPT ); Thu, 23 Aug 2012 11:22:06 -0400 Date: Thu, 23 Aug 2012 11:22:01 -0400 From: "J. Bruce Fields" To: Cyrill Gorcunov 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: <20120823152201.GB6923@fieldses.org> References: <20120823104323.040550004@openvz.org> <20120823104725.830795272@openvz.org> <20120823121230.GC29943@fieldses.org> <20120823123422.GB9112@moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120823123422.GB9112@moon> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3063 Lines: 72 On Thu, Aug 23, 2012 at 04:34:22PM +0400, Cyrill Gorcunov wrote: > 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. Fine, just make sure that's explained in the changelog. For distributors looking for patches to backport, "fix nil dereference" may set off alarm bells unnecessarily. --b. > --- > 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); > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/