Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932168AbVILThy (ORCPT ); Mon, 12 Sep 2005 15:37:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932169AbVILThx (ORCPT ); Mon, 12 Sep 2005 15:37:53 -0400 Received: from [66.228.95.230] ([66.228.95.230]:24193 "EHLO postage-due.permabit.com") by vger.kernel.org with ESMTP id S932168AbVILThx (ORCPT ); Mon, 12 Sep 2005 15:37:53 -0400 To: Valdis.Kletnieks@vt.edu Cc: linux-kernel@vger.kernel.org, marcelo.tosatti@cyclades.com Subject: Re: [PATCH] nfs client, kernel 2.4.31: readlink result overflow References: <78irx6wh6j.fsf@sober-counsel.permabit.com> <200509121846.j8CIk5YE025124@turing-police.cc.vt.edu> From: Assar Date: 12 Sep 2005 15:37:46 -0400 In-Reply-To: <200509121846.j8CIk5YE025124@turing-police.cc.vt.edu> Message-ID: <784q8qrsad.fsf@sober-counsel.permabit.com> User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Permabit-Spam: SKIPPED Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1307 Lines: 27 Valdis.Kletnieks@vt.edu writes: > Odd, as it has similar code - 2.6.13-mm1 nfs2xdr.c has: > /* Convert length of symlink */ > len = ntohl(*p++); > if (len >= rcvbuf->page_len || len <= 0) { To my reading, the 2.6.13 code does not copy the 4 bytes of length to rcvbuf. > Is there some *other* code in 2.6 that prevents this from being a problem, > if it's a problem on 2.4? > > > diff -u linux-2.4.31.orig/fs/nfs/nfs2xdr.c linux-2.4.31/fs/nfs/nfs2xdr.c > > --- linux-2.4.31.orig/fs/nfs/nfs2xdr.c 2002-11-28 18:53:15.000000000 -0500 > > +++ linux-2.4.31/fs/nfs/nfs2xdr.c 2005-09-07 17:36:04.000000000 -0400 > > @@ -571,8 +571,8 @@ > > strlen = (u32*)kmap(rcvbuf->pages[0]); > > /* Convert length of symlink */ > > len = ntohl(*strlen); > > - if (len > rcvbuf->page_len) > > - len = rcvbuf->page_len; > > + if (len > rcvbuf->page_len - 1 - 4) > > + len = rcvbuf->page_len - 1 - 4; > > Am I the only one who finds an uncommented "-1 -4" construct scary beyond belief? Probably not. What do you think looks better? sizeof(u32) ? - 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/