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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 BCA78C433E9 for ; Fri, 19 Feb 2021 08:27:27 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 24A5564EDB for ; Fri, 19 Feb 2021 08:27:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24A5564EDB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=weilnetz.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52872 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lD18H-0003QU-V1 for qemu-devel@archiver.kernel.org; Fri, 19 Feb 2021 03:27:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:56978) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lD178-0002qS-EP for qemu-devel@nongnu.org; Fri, 19 Feb 2021 03:26:15 -0500 Received: from mail.weilnetz.de ([37.120.169.71]:42420 helo=mail.v2201612906741603.powersrv.de) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lD172-0006B7-PY for qemu-devel@nongnu.org; Fri, 19 Feb 2021 03:26:13 -0500 Received: from edv-macbook-pro.fritz.box (p5b1511bf.dip0.t-ipconnect.de [91.21.17.191]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by mail.v2201612906741603.powersrv.de (Postfix) with ESMTPSA id E1E71DA06BD; Fri, 19 Feb 2021 09:26:03 +0100 (CET) Subject: Re: [PATCH] net: eepro100: validate various address values From: Stefan Weil To: P J P , Alexander Bulekov References: <20210218140629.373646-1-ppandit@redhat.com> <20210219015403.tl5upltt3d2bnmw5@mozz.bu.edu> <6qo84891-7or2-7p58-rr4-n2n46o5730rq@erqung.pbz> <00338810-b72e-6a9c-eef0-3c0adc764695@weilnetz.de> Message-ID: <43340d92-55da-61f2-5ad1-c8e3d6679f6d@weilnetz.de> Date: Fri, 19 Feb 2021 09:26:02 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <00338810-b72e-6a9c-eef0-3c0adc764695@weilnetz.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=37.120.169.71; envelope-from=sw@weilnetz.de; helo=mail.v2201612906741603.powersrv.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, NICE_REPLY_A=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Jason Wang , Li Qiang , Ruhr-University Bochum , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 19.02.21 um 09:08 schrieb Stefan Weil: > Okay, I can confirm the infinite recursion now. > > The test case triggers memory writes by the hardware which cause new > actions of the same hardware and so on. > > I don't know how the real hardware would handle that case. > > For QEMU we can extend the current code which tries to prevent endless > loops: the device status EEPRO100State can be extended by a recursion > counter to limit the number of recursions, or maybe a boolean flag > could be used to stop any recursion of action_command(). I prefer the > second variant (no recursion at all) and suggest to add a diagnostic > message as well like it is done for the endless loop case. If there are no recursions in normal use, the following patch should work: diff --git a/hw/net/eepro100.c b/hw/net/eepro100.c index 16e95ef9cc..2474cf3dc2 100644 --- a/hw/net/eepro100.c +++ b/hw/net/eepro100.c @@ -279,6 +279,9 @@ typedef struct {      /* Quasi static device properties (no need to save them). */      uint16_t stats_size;      bool has_extended_tcb_support; + +    /* Flag to avoid recursions. */ +    bool busy;  } EEPRO100State;  /* Word indices in EEPROM. */ @@ -837,6 +840,14 @@ static void action_command(EEPRO100State *s)         Therefore we limit the number of iterations. */      unsigned max_loop_count = 16; +    if (s->busy) { +        /* Prevent recursions. */ +        logout("recursion in %s:%u\n", __FILE__, __LINE__); +        return; +    } + +    s->busy = true; +      for (;;) {          bool bit_el;          bool bit_s; @@ -933,6 +944,7 @@ static void action_command(EEPRO100State *s)      }      TRACE(OTHER, logout("CU list empty\n"));      /* List is empty. Now CU is idle or suspended. */ +    s->busy = false;  }  static void eepro100_cu_command(EEPRO100State * s, uint8_t val)