Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932287AbYCFFkJ (ORCPT ); Thu, 6 Mar 2008 00:40:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755111AbYCFFjz (ORCPT ); Thu, 6 Mar 2008 00:39:55 -0500 Received: from cantor.suse.de ([195.135.220.2]:36885 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755051AbYCFFjy (ORCPT ); Thu, 6 Mar 2008 00:39:54 -0500 Date: Thu, 6 Mar 2008 06:39:50 +0100 From: Nick Piggin To: Andrew Morton Cc: stable@kernel.org, Kevin Coffman , Alexey Dobriyan , Linux Kernel Mailing List Subject: [patch] iov_iter_advance fix Message-ID: <20080306053950.GA28803@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2152 Lines: 71 iov_iter_advance skips over zero-length iovecs, however it does not properly terminate at the end of the iovec array. Fix this by checking against i->count before we skip a zero-length iov. The bug was reproduced with a test program that continually randomly creates iovs to writev. The fix was also verified with the same program and also it could verify that the correct data was contained in the file after each writev. 2.6.25 and 2.6.24.stable requires this fix. Signed-off-by: Nick Piggin Cc: stable@kernel.org --- Index: linux-2.6/mm/filemap.c =================================================================== --- linux-2.6.orig/mm/filemap.c 2008-03-06 08:46:38.000000000 +1100 +++ linux-2.6/mm/filemap.c 2008-03-06 08:48:00.000000000 +1100 @@ -1743,21 +1743,27 @@ } EXPORT_SYMBOL(iov_iter_copy_from_user); -static void __iov_iter_advance_iov(struct iov_iter *i, size_t bytes) +void iov_iter_advance(struct iov_iter *i, size_t bytes) { + BUG_ON(i->count < bytes); + if (likely(i->nr_segs == 1)) { i->iov_offset += bytes; + i->count -= bytes; } else { const struct iovec *iov = i->iov; size_t base = i->iov_offset; /* * The !iov->iov_len check ensures we skip over unlikely - * zero-length segments. + * zero-length segments (without overruning the iovec). */ - while (bytes || !iov->iov_len) { - int copy = min(bytes, iov->iov_len - base); + while (bytes || unlikely(!iov->iov_len && i->count)) { + int copy; + copy = min(bytes, iov->iov_len - base); + BUG_ON(!i->count || i->count < copy); + i->count -= copy; bytes -= copy; base += copy; if (iov->iov_len == base) { @@ -1769,14 +1775,6 @@ i->iov_offset = base; } } - -void iov_iter_advance(struct iov_iter *i, size_t bytes) -{ - BUG_ON(i->count < bytes); - - __iov_iter_advance_iov(i, bytes); - i->count -= bytes; -} EXPORT_SYMBOL(iov_iter_advance); /* -- 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/