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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C54B8C433F5 for ; Fri, 29 Apr 2022 06:41:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354748AbiD2Goc (ORCPT ); Fri, 29 Apr 2022 02:44:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52076 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354682AbiD2Gn4 (ORCPT ); Fri, 29 Apr 2022 02:43:56 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A499AB9F1B for ; Thu, 28 Apr 2022 23:40:37 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4KqN6S5MmNzCsLJ; Fri, 29 Apr 2022 14:36:00 +0800 (CST) Received: from huawei.com (10.175.124.27) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 29 Apr 2022 14:40:35 +0800 From: Miaohe Lin To: , CC: , , Subject: [PATCH 9/9] mm/z3fold: fix z3fold_page_migrate races with z3fold_map Date: Fri, 29 Apr 2022 14:40:51 +0800 Message-ID: <20220429064051.61552-10-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220429064051.61552-1-linmiaohe@huawei.com> References: <20220429064051.61552-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Think about the below scene: CPU1 CPU2 z3fold_page_migrate z3fold_map z3fold_page_trylock ... z3fold_page_unlock /* slots still points to old zhdr*/ get_z3fold_header get slots from handle get old zhdr from slots z3fold_page_trylock return *old* zhdr encode_handle(new_zhdr, FIRST|LAST|MIDDLE) put_page(page) /* zhdr is freed! */ but zhdr is still used by caller! z3fold_map can map freed z3fold page and lead to use-after-free bug. To fix it, we add PAGE_MIGRATED to indicate z3fold page is migrated and soon to be released. So get_z3fold_header won't return such page. Fixes: 1f862989b04a ("mm/z3fold.c: support page migration") Signed-off-by: Miaohe Lin --- mm/z3fold.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/mm/z3fold.c b/mm/z3fold.c index a7769befd74e..f41f8b0d9e9a 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -181,6 +181,7 @@ enum z3fold_page_flags { NEEDS_COMPACTING, PAGE_STALE, PAGE_CLAIMED, /* by either reclaim or free */ + PAGE_MIGRATED, /* page is migrated and soon to be released */ }; /* @@ -270,8 +271,13 @@ static inline struct z3fold_header *get_z3fold_header(unsigned long handle) zhdr = (struct z3fold_header *)(addr & PAGE_MASK); locked = z3fold_page_trylock(zhdr); read_unlock(&slots->lock); - if (locked) - break; + if (locked) { + struct page *page = virt_to_page(zhdr); + + if (!test_bit(PAGE_MIGRATED, &page->private)) + break; + z3fold_page_unlock(zhdr); + } cpu_relax(); } while (true); } else { @@ -389,6 +395,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless, clear_bit(NEEDS_COMPACTING, &page->private); clear_bit(PAGE_STALE, &page->private); clear_bit(PAGE_CLAIMED, &page->private); + clear_bit(PAGE_MIGRATED, &page->private); if (headless) return zhdr; @@ -1576,7 +1583,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa new_zhdr = page_address(newpage); memcpy(new_zhdr, zhdr, PAGE_SIZE); newpage->private = page->private; - page->private = 0; + set_bit(PAGE_MIGRATED, &page->private); z3fold_page_unlock(zhdr); spin_lock_init(&new_zhdr->page_lock); INIT_WORK(&new_zhdr->work, compact_page_work); @@ -1606,7 +1613,8 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work); - clear_bit(PAGE_CLAIMED, &page->private); + /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */ + page->private = 0; put_page(page); return 0; } -- 2.23.0