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Mon, 30 Jan 2023 23:00:33 GMT Received: from [10.110.113.14] (10.80.80.8) by nalasex01b.na.qualcomm.com (10.47.209.197) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.36; Mon, 30 Jan 2023 15:00:32 -0800 Message-ID: <63ef99b7-c6c4-497d-da08-a3966291de9f@quicinc.com> Date: Mon, 30 Jan 2023 15:00:32 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [RFC PATCH v2 12/22] sound: usb: card: Introduce USB SND platform op callbacks Content-Language: en-US To: Pierre-Louis Bossart , , , , , , , , , , , , , CC: , , , , , , References: <20230126031424.14582-1-quic_wcheng@quicinc.com> <20230126031424.14582-13-quic_wcheng@quicinc.com> <1013f667-c11f-25a2-ab2b-87b9368ad456@linux.intel.com> From: Wesley Cheng In-Reply-To: <1013f667-c11f-25a2-ab2b-87b9368ad456@linux.intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01b.na.qualcomm.com (10.47.209.197) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: YxBG3Jnkvw4vvbPrO9t0zF_PiC2Ra7GI X-Proofpoint-GUID: YxBG3Jnkvw4vvbPrO9t0zF_PiC2Ra7GI X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1 definitions=2023-01-30_17,2023-01-30_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 malwarescore=0 bulkscore=0 clxscore=1015 priorityscore=1501 adultscore=0 lowpriorityscore=0 mlxlogscore=762 impostorscore=0 phishscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2212070000 definitions=main-2301300211 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Pierre, On 1/26/2023 7:50 AM, Pierre-Louis Bossart wrote: > > > >> +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. > > Yep, will take a look at this a bit more to improve it. Thanks Wesley Cheng