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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?z/QHRj6A+BIi9FQAl7vjtBsl1covq43z1spqj1ZxkRXnwPNScC5iKEHEhrjz?= =?us-ascii?Q?j+ujtNXgsREAhNMLFp+JgrY++QxDoehLgB0uj1ElaWe05/UdsafxLZHFLNPO?= =?us-ascii?Q?FJgWjUhxFRrVbSJIzs/kq5cDRyfhGo1tIS8Ed5z3ARSZV/Z4xz8QLPkVv0gH?= =?us-ascii?Q?aIR8O/HxCMXjRfaQdg8YwLG2lxYlgBfU0RJaB183DiOrDregwvr22BGr4S38?= =?us-ascii?Q?yhe2zP5/Eb7j1Jk1sdYJMT7fyrtkZ49aQ9CwE5WEE2VCe6txTqJzH5o2HfrT?= =?us-ascii?Q?hmxWQuHyi/wcP5CKYoZY+uOIb8yMZ18xWejYiVwDYaDnclL0V/K1OO9+xrCB?= =?us-ascii?Q?NOZjBPoIJE74L5PWtyg3JHcCXRCLTB9LVtPi7jccs7jIA5NzFYy1tZpdOzw+?= =?us-ascii?Q?Hzc1Z8JWKwzrw37tR8jlVL95cBvUCBk/s42wAh3hd1h1tMTrdYf1tEWsOBWz?= =?us-ascii?Q?YNiHWJ00B93uJMWozYGOYQ7R79Kdp7T05P3wIVp0C6baOY0IJRBFjgCW3OnU?= =?us-ascii?Q?u68MU7JwqmcrrFPHGsXPP2O7s1VrwPTvL4maVF39m8tph837vDeuDcvVSwY6?= =?us-ascii?Q?JJyvryFo+TMgt37pw1V5hROJQIKJR17KcOiPTNAAD2ctsC6MNZ7GvMR68AIb?= =?us-ascii?Q?Z9pv3PDRqjSWK9Ly9dkfaiTLpLBRU+chOrRHbvFrPjF5yDtQzT/+lbwpb2Z1?= =?us-ascii?Q?D5Ws6z35Et4ulpy0TZPoVBmRUVOOU53t1FPEiwU+z0jbJQCa0T03wbXXsU7G?= =?us-ascii?Q?0Hr/NlsCs9qmdKnEQOzTw3mCCkxDucJD8mMzvQxGl38n035zOrjUBXOEjsPp?= =?us-ascii?Q?xeRGvJzWAsYhd7bS+1DJBCZFasDouYo5gFnlP+cf4pjh7GF67SzEElx9JNrQ?= =?us-ascii?Q?QyBfyuW2/G63sm+MdIZKlinc5UUYb7Ovfo4P0bUIDdeL2DiCyTTjb4XL9rur?= =?us-ascii?Q?02H+EH42yGT7BRTn+a2Cj+CdpGEPV4LtONijbbxccZlefW/tNpDl7bHZ+VUi?= =?us-ascii?Q?5H/IMp2Iv8JRPlhv7tgLUvM+A0VCyuIWg1VZmGHezt66hm/U1pyzTj7YdY/V?= =?us-ascii?Q?YeAAj1OqQh2bwc1QucYyBEcYycOlIy/wU7n8uWlS75Oe7QgjgokShH0cp3gk?= =?us-ascii?Q?Z84okaJmJNNgsWYvGHWnmFUdYu69F89nQ5WGoGJzt2HKCJcmwUjgRZlDEUV+?= =?us-ascii?Q?/wOZDKueMO4GI6R/egDdcI3ZRe7R1YjSsE+Kjkvj8q3hEiFYUjGys2lEPnHY?= =?us-ascii?Q?tCuJznSBwu/vvFbruj810gLonQrWZQVIyNJ9vtwOBX3AEQy0OGRXZARumDQv?= =?us-ascii?Q?fEIo/Qpq1nFIFRHHg2AH54hpYpteemiovtkFPryQw8P4uiVbxVcmwTKV1IyV?= =?us-ascii?Q?yo+umbGAuA5xLapRBCgAft3atZzY+02GPEExOO3wY+dcjIFuJ9JxmrVylMMe?= =?us-ascii?Q?zQxN5iBY3wpAGBCgudEjEUWz9aOJgMVZx14p3CxBAg5rt/12yadvEMWm1zbx?= =?us-ascii?Q?ZnM1KB224UEAqs0DWRonWoGllNQaGwWObkUSOaZP0FNcTd5di8jq1HQcUXzd?= =?us-ascii?Q?eJBseO/z5ZSVetVgjspNtLbZJgaiXwSDsC9+Do5w3OsGnBQrvsogQoRTqwiH?= =?us-ascii?Q?jhRSihaBOSqW79cjL9rdG8gZJNDBAj+/AkP84cILgsULu92fonQT1S/rg/ry?= =?us-ascii?Q?m96shoxuNysJQVNdHTnOzgQ2XVw6Ie8WaLb5cojXd4nHwO4u?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: bde7e850-e94b-4840-17f4-08df35fc37a0 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Oct 2026 20:35:49.3252 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: ncWNNYOQtFKW1U3fVADgGObDqMZAmPghZwmBNJUPTeM7tYqqCfOzp+szAk1T1R3xvlGv0MRTSLSlIdAkb5NJaQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW4PR12MB6924 On Thu, Oct 29, 2026 at 06:22:14AM +0000, Anil Kaushik wrote: > genl_bind() checks the GENL_MCAST_CAP_* flags of a group only when a > family owns it. For a group ID that no family owns, it returns 0, so any > user can join it. > > A family registered later can get that ID, and the socket stays a member: > nothing checks it again. An unprivileged user can join the free IDs, load > a family module with CTRL_CMD_GETFAMILY, which calls request_module(), > and then receive the notifications of a group with > GENL_MCAST_CAP_NET_ADMIN or GENL_MCAST_CAP_SYS_ADMIN. For example the > drop_monitor "events" group always gets ID 1, and is free until the > drop_monitor module is loaded. > > Fix by returning -ENOENT from genl_bind() when no family owns the group. > Nothing is ever sent to such a group, so joining it has no use. > > Found by the Sashiko review of the gtp multicast group fix. Tested as an > unprivileged user who joins all free IDs, then loads gtp and > drop_monitor: > > Before: > joins: ok=62 EPERM=2 > gtp/gtp (ID 15): member > NET_DM/events (ID 1): member > > After: > joins: ok=19 ENOENT=43 EPERM=2 > gtp/gtp (ID 15): not member > NET_DM/events (ID 1): not member > > Link: https://lore.kernel.org/netdev/179324692107.3134.14443689892607921337@kernel.org/ > Fixes: e03781879a0d ("drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group") > Signed-off-by: Anil Kaushik FWIW, this restores the behavior of commit 5ad6300524c0 ("genetlink: disallow subscribing to unknown mcast groups"). The entire function was later removed by commit 1e82a62fec61 ("genetlink: remove genl_bind") for unrelated reasons. So, given that the kernel already rejected such bindings between v3.19 and v5.7, I think that the potential for regressions is low. Reviewed-by: Ido Schimmel