From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762688AbYG3XoY (ORCPT ); Wed, 30 Jul 2008 19:44:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762514AbYG3Xna (ORCPT ); Wed, 30 Jul 2008 19:43:30 -0400 Received: from ns.suse.de ([195.135.220.2]:36444 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761936AbYG3Xn3 (ORCPT ); Wed, 30 Jul 2008 19:43:29 -0400 Date: Wed, 30 Jul 2008 16:27:47 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org, jejb@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Nick Piggin Subject: [patch 29/29] Fix off-by-one error in iov_iter_advance() Message-ID: <20080730232747.GD30670@suse.de> References: <20080730231003.655833364@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="fix-off-by-one-error-in-iov_iter_advance.patch" In-Reply-To: <20080730232451.GA30670@suse.de> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.25-stable review patch. If anyone has any objections, please let us know. ------------------ From: Linus Torvalds commit 94ad374a0751f40d25e22e036c37f7263569d24c upstream The iov_iter_advance() function would look at the iov->iov_len entry even though it might have iterated over the whole array, and iov was pointing past the end. This would cause DEBUG_PAGEALLOC to trigger a kernel page fault if the allocation was at the end of a page, and the next page was unallocated. The quick fix is to just change the order of the tests: check that there is any iovec data left before we check the iov entry itself. Thanks to Alexey Dobriyan for finding this case, and testing the fix. Reported-and-tested-by: Alexey Dobriyan Cc: Nick Piggin Cc: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1771,7 +1771,7 @@ void iov_iter_advance(struct iov_iter *i * The !iov->iov_len check ensures we skip over unlikely * zero-length segments (without overruning the iovec). */ - while (bytes || unlikely(!iov->iov_len && i->count)) { + while (bytes || unlikely(i->count && !iov->iov_len)) { int copy; copy = min(bytes, iov->iov_len - base); --