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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6F7DEC10F14 for ; Tue, 15 Oct 2019 20:25:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3A62B20872 for ; Tue, 15 Oct 2019 20:25:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571171110; bh=cNITrL0R424JvKCKW2ZKPmfFau8DO5shbDyf+rDzsYc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=IeX1qjDlyGJKkH9ZA5uZq7sznctkSw1UGaGaikPcBkPraJnK6r6mNSGJyOH2UXc9o ItiXHiCyF/XI9yUsfYiRZUp3XQiJaKwD4P6rdnoI1wz1imtgegL9QEWORxlWh1T1/b CSgXcErT37WeZ/9Uz1DtybCkI9N24Vt/zVW80UVo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729255AbfJOUZJ (ORCPT ); Tue, 15 Oct 2019 16:25:09 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:36682 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726491AbfJOUZJ (ORCPT ); Tue, 15 Oct 2019 16:25:09 -0400 Received: by mail-pl1-f196.google.com with SMTP id j11so10130712plk.3; Tue, 15 Oct 2019 13:25:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=6sUvpr0WehID8pP80ZhvLsnSYvQFqygK8r5rIP0jlhs=; b=lFw2H/d04tmnSUjS0uTmjPBEjbFYOOyTyG77Xpn90x3mUDRTuX2S1ZORxoelbYIBEV LxjXWKMg2mT1TOerkntyXB/2ZFZHIs8BFe5kI+FprTdedjNGUj+2n7uylGLqklxo2V/U E5003/iZC5RxGhMo7oMubgy1yOIdZKNg0qb9XfcJB3hVcmMs8VICx7Ma9/mfDCTH14FL GuAdgFvyEazpfFYeMFcL75VcLxUMM/gxzL+pYE8rk1awzAP6j2VZIcDrcDgVbmKy5bOS L+zbTMbAPHo0cZ8DYmyZ7mgoLOHjK5vp2fwoOY95Rh1o+SCRFRc4Wo0JkvgzgqkHn2Zg 02uQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=6sUvpr0WehID8pP80ZhvLsnSYvQFqygK8r5rIP0jlhs=; b=F4v3+MHVNPtilm1RWn0AYiBCi0gbpYlmNW8xexMVY0AGBqSPqnr2rh3+1ne4gf01YR ZllaUK0VxAM9MDhO/7bNoQWyCAMWopXfoNpI+jnNmZK1Q3suMvv5WRvMPSUgPhrOfDvF MBrud8k5mDvESA4GCjItPvZRhwZjrk/3aUpkaNNAPYmCs1/98XOFJBI8g4zvEJ2CyF4c lGbqxCwz67s/b4GKKtIL/7JwGROONpmIhdyglMhGAMnkqpJ8uWrNfcfw27voRM2hWDIb Xg6/2LDFW7Wl1bYSEj0l8Nl+pey2o33kjHRG1o2D93TZty23pznWyCsLqCzC6xLJ9aiy 3Vmw== X-Gm-Message-State: APjAAAXdiH15D/2zoaC9DjfcTMNfgGdu5nGl3fTsa5he+sWpq1jTv3/i DEtkB2/LZp0/ZezAA2/HBIg= X-Google-Smtp-Source: APXvYqwtfk//M4xoUiQ5GTOjTRH/d8dzRFbzMN73Qrnf7vvxbxpNaMTZrjExHyKgYQcjHbM4zH32sg== X-Received: by 2002:a17:902:b70f:: with SMTP id d15mr37719790pls.210.1571171108389; Tue, 15 Oct 2019 13:25:08 -0700 (PDT) Received: from google.com ([2620:15c:211:1:3e01:2939:5992:52da]) by smtp.gmail.com with ESMTPSA id u65sm18851477pgb.36.2019.10.15.13.25.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Oct 2019 13:25:07 -0700 (PDT) Date: Tue, 15 Oct 2019 13:25:05 -0700 From: Minchan Kim To: Chen Wandun , Andrew Morton Cc: ngupta@vflare.org, sergey.senozhatsky.work@gmail.com, axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] zram: fix race between backing_dev_show and backing_dev_store Message-ID: <20191015202505.GA246210@google.com> References: <1571046839-16814-1-git-send-email-chenwandun@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1571046839-16814-1-git-send-email-chenwandun@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Oct 14, 2019 at 05:53:59PM +0800, Chen Wandun wrote: > From: Chenwandun > > 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); > > get the value of zram->backing_dev too early in backing_dev_show, > that will result the value may be NULL at the begining, 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 > > Signed-off-by: Chenwandun It should be stable material. Cc: [4.14+] Acked-by: Minchan Kim Thanks!