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=-8.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,USER_IN_DEF_DKIM_WL 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 6CD5BC433F5 for ; Fri, 31 Aug 2018 20:17:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F5FC20837 for ; Fri, 31 Aug 2018 20:17:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="YfPCGbTp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F5FC20837 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727677AbeIAA02 (ORCPT ); Fri, 31 Aug 2018 20:26:28 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:37775 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727085AbeIAA01 (ORCPT ); Fri, 31 Aug 2018 20:26:27 -0400 Received: by mail-pf1-f193.google.com with SMTP id h69-v6so6003257pfd.4 for ; Fri, 31 Aug 2018 13:17:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=4opANQdSOR1YBQ2HptujUEqJpJcFQfDZPJWhmlJDjvY=; b=YfPCGbTpOH1x/zXEwZdcF+nHzpr+rdRPaHA6WJ08QdPXVFPAwvbr5TL0jtm7O0AeV7 WBM/94tD4YTJRzG+YJW/ILK+xZ+qO+b8t6K+xhsXM2v53UYb186GbN6Su0qtCmAGHe4c +cZG3Y0tfWH3YI3u4tqHPAIweGKhel9TOz/GDiFMiweP8YmfiiAaM2H+/5T9X8gJjv9z +C4wZHc97jBbwdqwuMUw8F7HsdVw+wm6ekzTixURzqAWFFyEwf5fqZSG2tvYbB6mzrS1 WFUjeUsFufMu1/SeNZBfAL3vbu5lbhFjF8+t0nvc1knPtEkkwO/EhR+uFZkcDIcSsGg4 F8CA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=4opANQdSOR1YBQ2HptujUEqJpJcFQfDZPJWhmlJDjvY=; b=jmgHd6/BckMcgde5NclM7Xi2+ThbAtT17aZHUkLzXbf9VNlOYJKx94aTXkXY2xuFti EAkdRSI4++Cc7+OsXnxH/2/kEtxZs/pcgafcW8xwbNsKX57q4eFk6aL5nGqrK4ayjZcC 9veJWQLsfX9CCN5ONr533BM5XE8xFO86hwdEt6ewtIoHyuOE/lFfSuxIhfmhNmXGSnuP B3iicc6UCLEf0BGVTdtiJZJMWe6v3x7aS80o46HuLG4XwE2JHaI4+MOKuCHrKxf7R6dr u/EeWXOTuKhNs9JnvJQh6KtkCy9uXl6wI5T+cb9R2jXBZtuhxacauNOSPnsCQtiLsIgW 9TVw== X-Gm-Message-State: APzg51Bxx+HlilIFU0rHCLXhffO08MqZjaFpz3SdnEdKmiVSf0v7Abf+ W+oS4kBDxvnrf6yk/vjevpOIiw== X-Google-Smtp-Source: ANB0VdZBhRg5FyZpzKO72M3/SEno9S7CpIDdCEs7gg5F7roMmQUG+slw2Dyug/g1OCOQ9ZtOhsbizQ== X-Received: by 2002:a62:4fd9:: with SMTP id f86-v6mr17707795pfj.110.1535746642188; Fri, 31 Aug 2018 13:17:22 -0700 (PDT) Received: from hackmann.mtv.corp.google.com ([2620:0:1000:1601:82f7:8f1:8c08:a97a]) by smtp.gmail.com with ESMTPSA id r1-v6sm28724100pfi.17.2018.08.31.13.17.21 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 Aug 2018 13:17:21 -0700 (PDT) Subject: Re: [PATCH] staging: android: ion: fix ION_IOC_{MAP,SHARE} use-after-free To: Greg Kroah-Hartman , Greg Hackmann Cc: linux-kernel@vger.kernel.org, Laura Abbott , Sumit Semwal , devel@driverdev.osuosl.org, kernel-team@android.com, stable@vger.kernel.org References: <20180831200627.59712-1-ghackmann@google.com> <20180831201232.GA23559@kroah.com> From: Greg Hackmann Message-ID: Date: Fri, 31 Aug 2018 13:17:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180831201232.GA23559@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/31/2018 01:12 PM, Greg Kroah-Hartman wrote: > On Fri, Aug 31, 2018 at 01:06:27PM -0700, Greg Hackmann wrote: >> The ION_IOC_{MAP,SHARE} ioctls drop and reacquire client->lock several >> times while operating on one of the client's ion_handles. This creates >> windows where userspace can call ION_IOC_FREE on the same client with >> the same handle, and effectively make the kernel drop its own reference. >> For example: >> >> - thread A: ION_IOC_ALLOC creates an ion_handle with refcount 1 >> - thread A: starts ION_IOC_MAP and increments the refcount to 2 >> - thread B: ION_IOC_FREE decrements the refcount to 1 >> - thread B: ION_IOC_FREE decrements the refcount to 0 and frees the >> handle >> - thread A: continues ION_IOC_MAP with a dangling ion_handle * to >> freed memory >> >> Fix this by holding client->lock for the duration of >> ION_IOC_{MAP,SHARE}, preventing the concurrent ION_IOC_FREE. Also >> remove ion_handle_get_by_id(), since there's literally no way to use it >> safely. >> >> This patch is applied on top of 4.9.y. Kernels 4.12 and later are >> unaffected, since all the underlying ion_handle infrastructure has been >> ripped out. > > Does 4.4.y or older also need this? If so, can you send backports, as > this one does not apply there. > > thanks, > > greg k-h > Yes, 4.4.y and older will need this. If there are no objections to this patch, I'll send backports ASAP.