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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 903ABC4321D for ; Wed, 22 Aug 2018 16:27:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 498122147A for ; Wed, 22 Aug 2018 16:27:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tziRTvpj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 498122147A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.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 S1727142AbeHVTxP (ORCPT ); Wed, 22 Aug 2018 15:53:15 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:38432 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726550AbeHVTxP (ORCPT ); Wed, 22 Aug 2018 15:53:15 -0400 Received: by mail-oi0-f65.google.com with SMTP id z185-v6so3732097oia.5 for ; Wed, 22 Aug 2018 09:27:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=reply-to:subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=5f674gdTOoYB4MOXo6SLNpTo0jpC34o3oO+PhVRILBc=; b=tziRTvpjczahyKqWb80CDI34DDBknsDOEWOfG/4CHFILRMZmxhTU/BuVzFF1x8ZqqE /WPXiIPmDLMIF8B+nZK29NWziV/JeTKRez6ZaInOVisUjpaZmWyktBzkM0agwBCxYz9n hGxsdTdCwOz7q9DbU7xolxvGFexk537bM1W/bZ23XTiYgJefm33x3X9ZqhAMc883gETI Mfz6cPBStL5jsZslYVmkVNPUibVT6WHjU3/2wk9LTzCnAtWPLrtkb/OFfofl9LWoMgpc xsz4b6VyIPZuUlE0Jyqf+wx86a1W+5RHBYat5T2LnV61Kek8OVBbrLM6rU8LKsTsSBWD 5W7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:subject:to:cc:references:from :message-id:date:user-agent:mime-version:in-reply-to :content-transfer-encoding:content-language; bh=5f674gdTOoYB4MOXo6SLNpTo0jpC34o3oO+PhVRILBc=; b=ASI/f+Xe2+f8xmNP4/Kfs1tCip/TubAhPDNXnxgY8c+faJBMHmHhAV+lzyyJBEgsjZ ucKoFkxEnPG5frfGGhKfxnvhClKorvWV9S3pKEM73KQMO/uFVzx/KycWL8t6GLyOggrZ yr1404NCoPfSfVW4Aji4oEF3flzjltFMBHcraoWNrwPxvjcL4GbwakDjLf/fUhqy9KBa pVBeMAKir9W6fgIAz8VsAZpb7tBe38wGL49us/KfUfSUWSHyBPJ91b6fl2irEpP96qL8 Cys7+dxR7KK7hxeHAZjHU9w35xO4vWP3tMPviCw5LD4vXPMRf5ZsSAdhluwdJ58zKyBF C88A== X-Gm-Message-State: APzg51B2TzwkQ8EOvF3npLVcWJvMtDXgz4GLSPfjGJt+PHhHS+VlDnQX xSckMsbH2RhlBBHQsZuV+elilX4= X-Google-Smtp-Source: ANB0VdZosweQ4av3vktHhFrQnJXnXwDU0MZMc+DkABIfOcnoqvytPuRp/1UJGcTyotFZc6y5LTBwog== X-Received: by 2002:aca:3ad4:: with SMTP id h203-v6mr4350118oia.294.1534955260895; Wed, 22 Aug 2018 09:27:40 -0700 (PDT) Received: from [192.168.27.3] ([47.184.170.128]) by smtp.gmail.com with ESMTPSA id s3-v6sm1115929oif.22.2018.08.22.09.27.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Aug 2018 09:27:40 -0700 (PDT) Reply-To: minyard@acm.org Subject: Re: [PATCH] Remove redundant cleanup in ipmi_register_smi To: Justin Ernst , Corey Minyard Cc: Arnd Bergmann , Greg Kroah-Hartman , Jeremy Kerr , openipmi-developer@lists.sourceforge.net, linux-kernel@vger.kernel.org, Russ Anderson References: <20180821152534.30367-1-justin.ernst@hpe.com> From: Corey Minyard Message-ID: <42513566-6982-c9c4-dbbb-ed98bd332fe9@gmail.com> Date: Wed, 22 Aug 2018 11:27:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180821152534.30367-1-justin.ernst@hpe.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/21/2018 10:25 AM, Justin Ernst wrote: > When ipmi_register_smi fails, it performs a small cleanup routine > before returning its error value. In try_smi_init, on the condition that > ipmi_register_smi fails, ipmi_unregister_smi is called. ipmi_unregister_smi > performs the same cleanup routine as ipmi_register_smi. This results in > a kernel NULL pointer dereference. Removing the cleanup routine in > ipmi_register_smi results in proper cleanup of a ipmi_register_smi failure. This is almost certainly wrong.  If ipmi_register_smi() fails, the calling code shouldn't call ipmi_unregister_smi(). However, I think I know what is going wrong.  ipmi_register_smi() can fail after the interface is initialized, if so the registering code will think it is registered and call ipmi_unregister_smi() on a failure.  I'll send a patch for this. -corey > > Cc: Corey Minyard > Cc: Arnd Bergmann > Cc: Greg Kroah-Hartman > Cc: Jeremy Kerr > Cc: openipmi-developer@lists.sourceforge.net > Cc: linux-kernel@vger.kernel.org > Cc: Russ Anderson > Acked-by: Andrew Banman > Signed-off-by: Justin Ernst > --- > drivers/char/ipmi/ipmi_msghandler.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c > index 51832b8a2c62..3b0b50c4f064 100644 > --- a/drivers/char/ipmi/ipmi_msghandler.c > +++ b/drivers/char/ipmi/ipmi_msghandler.c > @@ -3395,12 +3395,12 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers, > > out: > if (rv) { > - ipmi_bmc_unregister(intf); > - list_del_rcu(&intf->link); > + /* > + * ipmi_unregister_smi must be called to clean up after > + * failure. We unlock the mutex to allow ipmi_unregister_smi > + * to lock it and perform cleanup. > + */ > mutex_unlock(&ipmi_interfaces_mutex); > - synchronize_srcu(&ipmi_interfaces_srcu); > - cleanup_srcu_struct(&intf->users_srcu); > - kref_put(&intf->refcount, intf_free); > } else { > /* > * Keep memory order straight for RCU readers. Make