From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 808D6C64E8A for ; Thu, 3 Dec 2020 08:54:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E62022203 for ; Thu, 3 Dec 2020 08:54:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727473AbgLCIym (ORCPT ); Thu, 3 Dec 2020 03:54:42 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:8234 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387559AbgLCIyl (ORCPT ); Thu, 3 Dec 2020 03:54:41 -0500 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4CmqPG57Hgzkj4W; Thu, 3 Dec 2020 16:53:22 +0800 (CST) Received: from huawei.com (10.174.176.134) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Thu, 3 Dec 2020 16:53:50 +0800 From: Liu Zixian To: , , , , CC: , Subject: [PATCH v2] fix mmap return value when vma is merged after call_mmap() Date: Thu, 3 Dec 2020 16:53:50 +0800 Message-ID: <20201203085350.22624-1-liuzixian4@huawei.com> X-Mailer: git-send-email 2.21.0.windows.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.174.176.134] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On success, mmap should return the begin address of newly mapped area, but patch "mm: mmap: merge vma after call_mmap() if possible" set vm_start of newly merged vma to return value addr. Users of mmap will get wrong address if vma is merged after call_mmap(). We fix this by moving the assignment to addr before merging vma. Fixes: d70cec898324 ("mm: mmap: merge vma after call_mmap() if possible") Signed-off-by: Liu Zixian --- v2: We want to do "addr = vma->vm_start;" unconditionally, so move assignment to addr before if(unlikely) block. --- mm/mmap.c | 26 ++++++++++++-------------- 1 file changed, 12 insertions(+), 14 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index d91ecb00d38c..5c8b4485860d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1808,6 +1808,17 @@ unsigned long mmap_region(struct file *file, unsigned long addr, if (error) goto unmap_and_free_vma; + /* Can addr have changed?? + * + * Answer: Yes, several device drivers can do it in their + * f_op->mmap method. -DaveM + * Bug: If addr is changed, prev, rb_link, rb_parent should + * be updated for vma_link() + */ + WARN_ON_ONCE(addr != vma->vm_start); + + addr = vma->vm_start; + /* If vm_flags changed after call_mmap(), we should try merge vma again * as we may succeed this time. */ @@ -1822,25 +1833,12 @@ unsigned long mmap_region(struct file *file, unsigned long addr, fput(vma->vm_file); vm_area_free(vma); vma = merge; - /* Update vm_flags and possible addr to pick up the change. We don't - * warn here if addr changed as the vma is not linked by vma_link(). - */ - addr = vma->vm_start; + /* Update vm_flags to pick up the change. */ vm_flags = vma->vm_flags; goto unmap_writable; } } - /* Can addr have changed?? - * - * Answer: Yes, several device drivers can do it in their - * f_op->mmap method. -DaveM - * Bug: If addr is changed, prev, rb_link, rb_parent should - * be updated for vma_link() - */ - WARN_ON_ONCE(addr != vma->vm_start); - - addr = vma->vm_start; vm_flags = vma->vm_flags; } else if (vm_flags & VM_SHARED) { error = shmem_zero_setup(vma); -- 2.23.0