Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755083Ab1CKUqP (ORCPT ); Fri, 11 Mar 2011 15:46:15 -0500 Received: from kroah.org ([198.145.64.141]:46541 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754283Ab1CKUnE (ORCPT ); Fri, 11 Mar 2011 15:43:04 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Fri Mar 11 12:41:09 2011 Message-Id: <20110311204109.838126250@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Fri, 11 Mar 2011 12:40:06 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Hugh Dickins , Kerin Millar Subject: [05/17] mm: fix possible cause of a page_mapped BUG In-Reply-To: <20110311204126.GA7223@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1875 Lines: 53 2.6.32-longterm 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; } /* -- 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/