From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 3C8136B02B8 for ; Mon, 11 Sep 2017 07:05:17 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id t3so16244803pgt.7 for ; Mon, 11 Sep 2017 04:05:17 -0700 (PDT) Received: from EUR03-VE1-obe.outbound.protection.outlook.com (mail-eopbgr50104.outbound.protection.outlook.com. [40.107.5.104]) by mx.google.com with ESMTPS id f5si5643785pgq.140.2017.09.11.04.05.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 11 Sep 2017 04:05:15 -0700 (PDT) Subject: [PATCH] ksm: Fix unlocked iteration over vmas in cmp_and_merge_page() From: Kirill Tkhai Date: Mon, 11 Sep 2017 14:05:05 +0300 Message-ID: <150512788393.10691.8868381099691121308.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, aarcange@redhat.com, minchan@kernel.org, mhocko@suse.com, zhongjiang@huawei.com, mingo@kernel.org, imbrenda@linux.vnet.ibm.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ktkhai@virtuozzo.com In this place mm is unlocked, so vmas or list may change. Down read mmap_sem to protect them from modifications. Signed-off-by: Kirill Tkhai (and compile-tested-by) --- mm/ksm.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/ksm.c b/mm/ksm.c index db20f8436bc3..86f0db3d6cdb 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1990,6 +1990,7 @@ static void stable_tree_append(struct rmap_item *rmap_item, */ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) { + struct mm_struct *mm = rmap_item->mm; struct rmap_item *tree_rmap_item; struct page *tree_page = NULL; struct stable_node *stable_node; @@ -2062,9 +2063,11 @@ static void cmp_and_merge_page(struct page *page, struct rmap_item *rmap_item) if (ksm_use_zero_pages && (checksum == zero_checksum)) { struct vm_area_struct *vma; - vma = find_mergeable_vma(rmap_item->mm, rmap_item->address); + down_read(&mm->mmap_sem); + vma = find_mergeable_vma(mm, rmap_item->address); err = try_to_merge_one_page(vma, page, ZERO_PAGE(rmap_item->address)); + up_read(&mm->mmap_sem); /* * In case of failure, the page was not really empty, so we * need to continue. Otherwise we're done. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org