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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 78A12CA9EC9 for ; Mon, 4 Nov 2019 21:52:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EC6B217F5 for ; Mon, 4 Nov 2019 21:52:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904338; bh=Ew1uxJTVJthNfzNREG7gYLsWwvyHdnXZixxGGJqsyBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=V3hW44GzZY2UjNY3M4/GTyIKz404HSIR5kcXuCOM6LmvtyNypaI+ua9UcjqNLVgqa VaWGseh8AMFp93euyVc3YX2BVvshkkaaEsQF+Hp6MjX8pDlmjMp+J90qRChzhuGa+n FocgGP0YLyXWCViITsGT5SBy1J10Y1Dgpyi8qRuE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730717AbfKDVwR (ORCPT ); Mon, 4 Nov 2019 16:52:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:45552 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730690AbfKDVwM (ORCPT ); Mon, 4 Nov 2019 16:52:12 -0500 Received: from localhost (6.204-14-84.ripe.coltfrance.com [84.14.204.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3E2E8217F5; Mon, 4 Nov 2019 21:52:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572904331; bh=Ew1uxJTVJthNfzNREG7gYLsWwvyHdnXZixxGGJqsyBc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UkcK20AvDSgUvxLkTjh+zLb+TvyollYHzaHN7vzsqFvoD2BRUXdT6N5bOAH6QBqmj GczXFe4FH3TlhPgr1hyakHl3jBKmiXNOUoyn6lgKhKC45aiDwYN7ek6KerryfwdiFw FAu1WXcc3ivSTWbAO8piLuHSdU/sTZaSwCuHLa30= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chenwandun , Minchan Kim , Sergey Senozhatsky , Jens Axboe , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 01/95] zram: fix race between backing_dev_show and backing_dev_store Date: Mon, 4 Nov 2019 22:43:59 +0100 Message-Id: <20191104212038.811379835@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191104212038.056365853@linuxfoundation.org> References: <20191104212038.056365853@linuxfoundation.org> User-Agent: quilt/0.66 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit f7daefe4231e57381d92c2e2ad905a899c28e402 ] CPU0: CPU1: backing_dev_show backing_dev_store ...... ...... file = zram->backing_dev; down_read(&zram->init_lock); down_read(&zram->init_init_lock) file_path(file, ...); zram->backing_dev = backing_dev; up_read(&zram->init_lock); up_read(&zram->init_lock); gets the value of zram->backing_dev too early in backing_dev_show, which resultin the value being NULL at the beginning, and not NULL later. backtrace: d_path+0xcc/0x174 file_path+0x10/0x18 backing_dev_show+0x40/0xb4 dev_attr_show+0x20/0x54 sysfs_kf_seq_show+0x9c/0x10c kernfs_seq_show+0x28/0x30 seq_read+0x184/0x488 kernfs_fop_read+0x5c/0x1a4 __vfs_read+0x44/0x128 vfs_read+0xa0/0x138 SyS_read+0x54/0xb4 Link: http://lkml.kernel.org/r/1571046839-16814-1-git-send-email-chenwandun@huawei.com Signed-off-by: Chenwandun Acked-by: Minchan Kim Cc: Sergey Senozhatsky Cc: Jens Axboe Cc: [4.14+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- drivers/block/zram/zram_drv.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 133178c9b2cf3..1b4e195c0d3c9 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -291,13 +291,14 @@ static void reset_bdev(struct zram *zram) static ssize_t backing_dev_show(struct device *dev, struct device_attribute *attr, char *buf) { + struct file *file; struct zram *zram = dev_to_zram(dev); - struct file *file = zram->backing_dev; char *p; ssize_t ret; down_read(&zram->init_lock); - if (!zram_wb_enabled(zram)) { + file = zram->backing_dev; + if (!file) { memcpy(buf, "none\n", 5); up_read(&zram->init_lock); return 5; -- 2.20.1