From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932730Ab1DYUlx (ORCPT ); Mon, 25 Apr 2011 16:41:53 -0400 Received: from 1wt.eu ([62.212.114.60]:34368 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932253Ab1DYUYy (ORCPT ); Mon, 25 Apr 2011 16:24:54 -0400 Message-Id: <20110425200236.079177121@pcw.home.local> User-Agent: quilt/0.48-1 Date: Mon, 25 Apr 2011 22:03:43 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@kernel.org, stable-review@kernel.org Cc: Hugh Dickins , Linus Torvalds , Kerin Millar , Greg Kroah-Hartman Subject: [PATCH 071/173] mm: fix possible cause of a page_mapped BUG In-Reply-To: <46075c3a3ef08be6d70339617d6afc98@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.27.59-stable review patch. If anyone has any objections, please let us know. ------------------ From: Hugh Dickins commit a3e8cc643d22d2c8ed36b9be7d9c9ca21efcf7f7 upstream. Robert Swiecki reported a BUG_ON(page_mapped) from a fuzzer, punching a hole with madvise(,, MADV_REMOVE). That path is under mutex, and cannot be explained by lack of serialization in unmap_mapping_range(). Reviewing the code, I found one place where vm_truncate_count handling should have been updated, when I switched at the last minute from one way of managing the restart_addr to another: mremap move changes the virtual addresses, so it ought to adjust the restart_addr. But rather than exporting the notion of restart_addr from memory.c, or converting to restart_pgoff throughout, simply reset vm_truncate_count to 0 to force a rescan if mremap move races with preempted truncation. We have no confirmation that this fixes Robert's BUG, but it is a fix that's worth making anyway. Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds Cc: Kerin Millar Signed-off-by: Greg Kroah-Hartman --- mm/mremap.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/mm/mremap.c +++ b/mm/mremap.c @@ -92,9 +92,7 @@ static void move_ptes(struct vm_area_str */ mapping = vma->vm_file->f_mapping; spin_lock(&mapping->i_mmap_lock); - if (new_vma->vm_truncate_count && - new_vma->vm_truncate_count != vma->vm_truncate_count) - new_vma->vm_truncate_count = 0; + new_vma->vm_truncate_count = 0; } /*