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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86794C61DA2 for ; Thu, 26 Jan 2023 16:26:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232731AbjAZQ0K (ORCPT ); Thu, 26 Jan 2023 11:26:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33796 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232734AbjAZQ0E (ORCPT ); Thu, 26 Jan 2023 11:26:04 -0500 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4E2071659; Thu, 26 Jan 2023 08:25:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674750321; x=1706286321; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=vQ5Xq73A77dcWgvpi3junj6Bi2A1oCr2o7H27eKOWOQ=; b=Dos9LDbJJAJWVBAuxEsqIAE/UTLCxaf0teAPFdehrq7/uyLDmvpyetUp T0XmGyejuTrvChUuPl8gM0PTmB3tZkUiNYmRi6h0Zqp/nqKlcTYQSozhE IVkkB2BvveIoq8tHKNXPm+FtaAvRunuF9o0G/7sKaGFwRSIHwcJYhLkvC 9/xCp/ohqE1ClwICbBz6Tp0YMF09oNkEsAxpHCPRypPfqQQaj64ki/T+i m5Qp5Zh0U7SGj7x+SfLs6at+j4Wztpav7qwt/UIp13c9Yp6Sn4H/OvhsX 0IJRO7K5L9eH8xoQsJgXfuiz21rjLtjHOrFRjSwMRTdMCKr72NetNzfi7 A==; X-IronPort-AV: E=McAfee;i="6500,9779,10602"; a="354154664" X-IronPort-AV: E=Sophos;i="5.97,248,1669104000"; d="scan'208";a="354154664" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2023 08:24:38 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10602"; a="612855067" X-IronPort-AV: E=Sophos;i="5.97,248,1669104000"; d="scan'208";a="612855067" Received: from nmani1-mobl2.amr.corp.intel.com (HELO [10.209.167.178]) ([10.209.167.178]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jan 2023 08:24:36 -0800 Message-ID: <1013f667-c11f-25a2-ab2b-87b9368ad456@linux.intel.com> Date: Thu, 26 Jan 2023 09:50:14 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.4.2 Subject: Re: [RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform op callbacks Content-Language: en-US To: Wesley Cheng , srinivas.kandagatla@linaro.org, mathias.nyman@intel.com, perex@perex.cz, lgirdwood@gmail.com, andersson@kernel.org, krzysztof.kozlowski+dt@linaro.org, gregkh@linuxfoundation.org, Thinh.Nguyen@synopsys.com, broonie@kernel.org, bgoswami@quicinc.com, tiwai@suse.com, robh+dt@kernel.org, agross@kernel.org Cc: devicetree@vger.kernel.org, alsa-devel@alsa-project.org, linux-arm-msm@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, quic_jackp@quicinc.com, quic_plai@quicinc.com References: <20230126031424.14582-1-quic_wcheng@quicinc.com> <20230126031424.14582-13-quic_wcheng@quicinc.com> From: Pierre-Louis Bossart In-Reply-To: <20230126031424.14582-13-quic_wcheng@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org > +int snd_usb_register_platform_ops(struct snd_usb_platform_ops *ops) > +{ > + if (platform_ops) > + return -EEXIST; > + > + platform_ops = ops; > + return 0; > +} > +EXPORT_SYMBOL_GPL(snd_usb_register_platform_ops); > + > +int snd_usb_unregister_platform_ops(void) > +{ > + platform_ops = NULL; > + return 0; > +} > +EXPORT_SYMBOL_GPL(snd_usb_unregister_platform_ops); I find this super-racy. If the this function is called just before ... > > /* > * disconnect streams > @@ -910,6 +928,10 @@ static int usb_audio_probe(struct usb_interface *intf, > usb_set_intfdata(intf, chip); > atomic_dec(&chip->active); > mutex_unlock(®ister_mutex); > + > + if (platform_ops->connect_cb) > + platform_ops->connect_cb(intf, chip); > + ... this, then you have a risk of using a dandling pointer. You also didn't test that the platform_ops != NULL, so there's a risk of dereferencing a NULL pointer. Not so good, eh? It's a classic (I've had the same sort of issues with SoundWire), when you export ops from one driver than can be removed, then additional protection is needed when using those callbacks.