Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933503Ab0BDR03 (ORCPT ); Thu, 4 Feb 2010 12:26:29 -0500 Received: from kroah.org ([198.145.64.141]:34937 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933364Ab0BDRW1 (ORCPT ); Thu, 4 Feb 2010 12:22:27 -0500 X-Mailbox-Line: From linux@linux.site Thu Feb 4 09:15:24 2010 Message-Id: <20100204171524.332399752@linux.site> User-Agent: quilt/0.47-14.9 Date: Thu, 04 Feb 2010 09:12:35 -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, Anfei , Russell King , Miklos Szeredi , Nick Piggin , , Greg Kroah-Hartman Subject: [64/74] mm: flush dcache before writing into page to avoid alias In-Reply-To: <20100204171850.GA16539@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2507 Lines: 81 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: anfei zhou commit 931e80e4b3263db75c8e34f078d22f11bbabd3a3 upstream. The cache alias problem will happen if the changes of user shared mapping is not flushed before copying, then user and kernel mapping may be mapped into two different cache line, it is impossible to guarantee the coherence after iov_iter_copy_from_user_atomic. So the right steps should be: flush_dcache_page(page); kmap_atomic(page); write to page; kunmap_atomic(page); flush_dcache_page(page); More precisely, we might create two new APIs flush_dcache_user_page and flush_dcache_kern_page to replace the two flush_dcache_page accordingly. Here is a snippet tested on omap2430 with VIPT cache, and I think it is not ARM-specific: int val = 0x11111111; fd = open("abc", O_RDWR); addr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); *(addr+0) = 0x44444444; tmp = *(addr+0); *(addr+1) = 0x77777777; write(fd, &val, sizeof(int)); close(fd); The results are not always 0x11111111 0x77777777 at the beginning as expected. Sometimes we see 0x44444444 0x77777777. Signed-off-by: Anfei Cc: Russell King Cc: Miklos Szeredi Cc: Nick Piggin Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/fuse/file.c | 3 +++ mm/filemap.c | 3 +++ 2 files changed, 6 insertions(+) --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -828,6 +828,9 @@ static ssize_t fuse_fill_write_pages(str if (!page) break; + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + pagefault_disable(); tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes); pagefault_enable(); --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2253,6 +2253,9 @@ again: if (unlikely(status)) break; + if (mapping_writably_mapped(mapping)) + flush_dcache_page(page); + pagefault_disable(); copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes); pagefault_enable(); -- 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/