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Miller" , "John W. Linville" , netdev@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH net] nfc: avoid potential race condition Message-ID: <20210927121427.GE2048@kadam> References: <20210923065051.GA25122@kili> <3760c70c-299c-89bf-5a4a-22e8d564ef92@canonical.com> <20210923122220.GB2083@kadam> <47358bea-e761-b823-dfbd-cd8e0a2a69a6@canonical.com> <20210924131441.6598ba3a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210924131441.6598ba3a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-ClientProxiedBy: JN2P275CA0016.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:3::28) To MWHPR1001MB2365.namprd10.prod.outlook.com (2603:10b6:301:2d::28) MIME-Version: 1.0 Received: from kadam (62.8.83.99) by JN2P275CA0016.ZAFP275.PROD.OUTLOOK.COM (2603:1086:0:3::28) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4544.13 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?X8uB9RzsSp4FZywONpzNhomPq+DjD6EIpqd8d1Xx+PWy/LqmJ5F7iQcpi6jc?= =?us-ascii?Q?ln9qCRPQF+4z61aZAHGEIpqzvgQfE+DncWWZOzv69y//kKYyEpiTcAZr1xY5?= =?us-ascii?Q?dBWaabnXjavjDQQKKbmdVGrSzSmbcspBnBhvu9osoBFFHVNKqrJJzuN54InZ?= =?us-ascii?Q?+MHYBATlbk7haSPn+oYMZNCkQzT3zfKdEE5gKMmUSReBK42rEK65dhvSJXb7?= =?us-ascii?Q?D0FjDLmQlLpeTTcuejwjkAWgaDuAITLh9yDYs0Yrg5PrnlDPqflmIHX+6s7C?= =?us-ascii?Q?tc27IULQrZSm9mXzuAtbDsS1rZ7KMIWY++08hh7PqVAE3ngp/dgs02pIJnnJ?= =?us-ascii?Q?WcA5gbBpbZkkDNC3x4wv41mv/H7hMAwQPpAwz1hSM5Xo7IL0taWC5ZLTiq0a?= =?us-ascii?Q?21cpSsuAL3Yh3J1AHxTpGboxGQEefWgRDuDF+usY64v+0+5/13qV2UtEGZdA?= =?us-ascii?Q?K/y1n1oYed2GTb/XfOGH/+FT4tYGLpd0TXbcVMGAt9Db7rgQ260ExSt/Qo8v?= =?us-ascii?Q?lrfibTwQv5qW2R/PZXiNORpZRfux2ERgOcgF6464ukh/lFC85yt+SJxYRT1+?= =?us-ascii?Q?wqulmk7tH5I4PNYeiuU4GXTV3dwSrhO//nnqhMFoB/VyEOsxo3s3RRY/5fps?= =?us-ascii?Q?KrMGOHoTA2AhdFMWQPevNpZHM/5FLF1ZomdoLb92p7oJO8GRKFCOk+KVs2vF?= =?us-ascii?Q?yyF8ba3dMKzmbzkCAMgUJCABJ0e7dRtU03meEGLwDxWeiOvzKooY10FhNhII?= =?us-ascii?Q?O0DT0WotGcQLRE3jCNZs50ZUTYNJ9GU72SGwjVkaMrrGIzeOwhU98pILuOp/?= =?us-ascii?Q?l8sczKJTMER9yTMt2FNO5zktFVLW6VHojEQXIWXwepz3XqsWz4+mydpIteG7?= =?us-ascii?Q?+mHd3nvbgtejDuJ3iU21MHBHSDrLoZ3Fcd9b13jiBNwhGaTKLktugesmxtta?= =?us-ascii?Q?y8aj8C22Qdd6VMO8kOffJfN+XzMEJrGfPanxMzczntZv9MhV+uFVPF18OdkX?= =?us-ascii?Q?S4uhMY65h4jwt/DPIGwOndmVwj8UdySzA1qgsFCpj0IsjYZovurtaf23GyGT?= =?us-ascii?Q?lq9hHdDETxwkVG3oTC6abVrktbBKSyjQRkOANG6GvDkuNYhrZvDbRagvQXe3?= =?us-ascii?Q?TKhGp3wKZbQz6EZcTN6uE6ysJ/s97DMSEBDu0tveHbcI/C3jgmD+pN2//riw?= =?us-ascii?Q?3uVQGvWHNGf2ayq0woHGmsnP6TcHonO4nTAUb0oWfd4B58dRlNxy5npVh4qC?= =?us-ascii?Q?e/eV71WaD6jewY+9H2xodH57wF9uiCI/pPkP0yLn0gRayXhECWJVMDEiAr2K?= =?us-ascii?Q?8eT8gXgDXs2K6dydycgHKFyi?= X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: a43e9f35-62a3-4647-7281-08d981b0675f X-MS-Exchange-CrossTenant-AuthSource: MWHPR1001MB2365.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Sep 2021 12:14:50.2898 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 2++0bl7HlgoQhIsjCzammwae+UphHSR6KQ5y3O83Dt5ifTYl6ychjAPmZ+Ky/rLpwimWhiOci3l6l/y3tVP8aVQQWheZBmEB+hP/JGRRKNQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR10MB1294 X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10119 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 adultscore=0 mlxscore=0 malwarescore=0 spamscore=0 phishscore=0 bulkscore=0 mlxlogscore=901 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2109270084 X-Proofpoint-ORIG-GUID: dDz3ELSdJ_YInj7EyW3RM56CcodwiSJK X-Proofpoint-GUID: dDz3ELSdJ_YInj7EyW3RM56CcodwiSJK Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Sep 24, 2021 at 01:14:41PM -0700, Jakub Kicinski wrote: > On Fri, 24 Sep 2021 10:21:33 +0200 Krzysztof Kozlowski wrote: > > On 23/09/2021 14:22, Dan Carpenter wrote: > > > On Thu, Sep 23, 2021 at 09:26:51AM +0200, Krzysztof Kozlowski wrote: > > >> On 23/09/2021 08:50, Dan Carpenter wrote: > > [...] > > >> > > >> I think the difference between this llcp_sock code and above transport, > > >> is lack of writer to llcp_sock->local with whom you could race. > > >> > > >> Commits c0cfa2d8a788fcf4 and 6a2c0962105ae8ce causing the > > >> multi-transport race show nicely assigns to vsk->transport when module > > >> is unloaded. > > >> > > >> Here however there is no writer to llcp_sock->local, except bind and > > >> connect and their error paths. The readers which you modify here, have > > >> to happen after bind/connect. You cannot have getsockopt() or release() > > >> before bind/connect, can you? Unless you mean here the bind error path, > > >> where someone calls getsockopt() in the middle of bind()? Is it even > > >> possible? > > >> > > > > > > I don't know if this is a real issue either. > > > > > > Racing with bind would be harmless. The local pointer would be NULL and > > > it would return harmlessly. You would have to race with release and > > > have a third trying to release local devices. (Again that might be > > > wild imagination. It may not be possible). > > > > Indeed. The code looks reasonable, though, so even if race is not really > > reproducible: > > > > Reviewed-by: Krzysztof Kozlowski > > Would you mind making a call if this is net (which will mean stable) or > net-next material (without the Fixes tags) and reposting? Thanks! :) This should be ported to stable. The race is condition is real because ->release() can race with itself. I don't know if expliotable or not beyond just a denial of service. regards, dan carpenter