From patchwork Mon Apr 26 12:33:16 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12224217 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 DD7A9C433B4 for ; Mon, 26 Apr 2021 12:34:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5D976611C1 for ; Mon, 26 Apr 2021 12:34:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D976611C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0DC376B0072; Mon, 26 Apr 2021 08:33:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0656D6B0073; Mon, 26 Apr 2021 08:33:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD1EE6B0074; Mon, 26 Apr 2021 08:33:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0036.hostedemail.com [216.40.44.36]) by kanga.kvack.org (Postfix) with ESMTP id C11D76B0072 for ; Mon, 26 Apr 2021 08:33:56 -0400 (EDT) Received: from smtpin31.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 7A75F18024CD4 for ; Mon, 26 Apr 2021 12:33:56 +0000 (UTC) X-FDA: 78074460072.31.6B6E8FA Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf10.hostedemail.com (Postfix) with ESMTP id 1D77440002DA for ; Mon, 26 Apr 2021 12:33:46 +0000 (UTC) Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FTPQQ3VvCz19MM8; Mon, 26 Apr 2021 20:31:26 +0800 (CST) Received: from huawei.com (10.175.104.170) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.498.0; Mon, 26 Apr 2021 20:33:44 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , , Subject: [PATCH v6 4/4] mm/shmem: fix shmem_swapin() race with swapoff Date: Mon, 26 Apr 2021 20:33:16 +0800 Message-ID: <20210426123316.806267-5-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210426123316.806267-1-linmiaohe@huawei.com> References: <20210426123316.806267-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.104.170] X-CFilter-Loop: Reflected X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 1D77440002DA X-Stat-Signature: w57p4nuab86xns6kfexk7s5rwqg8n68z Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=szxga04-in.huawei.com; client-ip=45.249.212.190 X-HE-DKIM-Result: none/none X-HE-Tag: 1619440426-139057 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When I was investigating the swap code, I found the below possible race window: CPU 1 CPU 2 ----- ----- shmem_swapin swap_cluster_readahead if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) { swapoff .. si->swap_file = NULL; .. struct inode *inode = si->swap_file->f_mapping->host;[oops!] Close this race window by using get/put_swap_device() to guard against concurrent swapoff. Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not") Reviewed-by: "Huang, Ying" Signed-off-by: Miaohe Lin --- mm/shmem.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/mm/shmem.c b/mm/shmem.c index 26c76b13ad23..e5dd8fa51463 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1696,7 +1696,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, struct address_space *mapping = inode->i_mapping; struct shmem_inode_info *info = SHMEM_I(inode); struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm; - struct page *page; + struct swap_info_struct *si; + struct page *page = NULL; swp_entry_t swap; int error; @@ -1704,6 +1705,12 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, swap = radix_to_swp_entry(*pagep); *pagep = NULL; + /* Prevent swapoff from happening to us. */ + si = get_swap_device(swap); + if (!si) { + error = EINVAL; + goto failed; + } /* Look it up and read it in.. */ page = lookup_swap_cache(swap, NULL, 0); if (!page) { @@ -1765,6 +1772,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, swap_free(swap); *pagep = page; + if (si) + put_swap_device(si); return 0; failed: if (!shmem_confirm_swap(mapping, index, swap)) @@ -1775,6 +1784,9 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, put_page(page); } + if (si) + put_swap_device(si); + return error; }