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Miller" , Jakub Kicinski , Paolo Abeni , David Ahern , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Taehee Yoo Subject: Re: [PATCH v2 net 1/5] ipv6: mcast: fix RCU list diversion in ip6_mc_del1_src() Message-ID: <20260830154406.GA2974032@shredder> References: <20260828084531.1826790-1-edumazet@google.com> <20260828084531.1826790-2-edumazet@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828084531.1826790-2-edumazet@google.com> X-ClientProxiedBy: FR2P281CA0088.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:9b::13) To PH0PR12MB7957.namprd12.prod.outlook.com (2603:10b6:510:281::22) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB7957:EE_|IA1PR12MB8223:EE_ X-MS-Office365-Filtering-Correlation-Id: 9ca0fce6-a8c7-4a9b-bdb5-08df06ad8c1b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|23010399003|366016|56012099006|10067099003|11063799006|4143699003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?UYmYEs3g78/HWzNlhrOzLfN9HekJTqLrOyBK9xubftidQH07I8OEkOsGxX47?= =?us-ascii?Q?Ack/y/SgRABXHOUesYmIAYUI1L5enoJ+/R9fEhjY5hgKT5oCTDoSyaL+wMNE?= =?us-ascii?Q?bTOGCoe6vgGfahmEuKSK302V+RE8OZ1kyH4V6e6Eymx4DXloqvwgRq4l0a7C?= =?us-ascii?Q?G+5sI9/2MsxhBMRoRztMFXlxxqlSM7Eh3OgaURxTc++85r1Q5/j3VjaGYIRK?= =?us-ascii?Q?a1nwtH7ef8Cl7+3wkQcyb/3WlfbKfdFHucNfXNNQtEcHCv2B0SQWSXxWitzi?= =?us-ascii?Q?dFjirDfUNoQRQU9XkjD7DaczKO5gOfh7P9athUvHkvX59G2TfGr42kjuZ0d5?= =?us-ascii?Q?amqVQSthSzUkFqjw8/w/wVs8HxI4MVDV9sYY3az0SUvYv9bkQ2c3kM/l3Gkz?= =?us-ascii?Q?VxWe12g8qgmgyL7449P87ntLFiGPC0nJegI5Olne/PsNqnyMpK0EWfzFEGQG?= =?us-ascii?Q?dAohD7sIZUQmC5bMOnQW9zI3aOcOTppMRwz7bg/HSjGM077NxJl6DJ58AQmu?= =?us-ascii?Q?D3xhfGubct+YQXpqzhbQgtRV0dWdiohu5rxLfaUU/+HMkXz1PwkcwHIolsck?= =?us-ascii?Q?yYlESS/C2aVDNrx2S9UmtMeVNgnnkLdli2kQuOzjTw02Q9XGN9eFjOso+jwY?= =?us-ascii?Q?uvYwF+esDEoD0bonFxphU2OMyM2wniHcZqnzenTznPRY0gwZfbJ7FjU8pah/?= =?us-ascii?Q?J0a15Kgy1lQ8z5OFVDuapt7crlzpHRUFwZPuw3alTUfNAgCBd2y45OdTZwQp?= =?us-ascii?Q?Pt3VfTDC3I6ucdDMS5y8T7YPEQTawd0udXk7VEVQ7McajnQWRs9yJmF9ruT3?= =?us-ascii?Q?yQ2pFCATcT161je9jMeEba5VLsEhEr+/nA/t/t0WjkesG6k8aIrxhMImWRF7?= =?us-ascii?Q?w90fwS7Bse7NE4oPwGpEXg5pPxFIbAeR3GHxCj2LiZN9jRbdHnc/z2IrFiR0?= =?us-ascii?Q?MP1ybKrA3YZgtso+dgrSKf9ytD/VyYdQD+RG7IaYFBTZblaT5hx9xDCdcjEj?= =?us-ascii?Q?/xoaQzePfVv+Qr7fjMFwoObQn2A4gb1V35nkR3B2Vwe1VHxNfgpYNR3BT8kC?= =?us-ascii?Q?snQjHWTA4vIueSi1fdYW9xoxIlFQ6ro2fHnuLO73ZhV/2d8qNb7+O44Vp2Og?= =?us-ascii?Q?geGh62f2H6vSbZoEQmYz8cJbfinTuEiY7glXqW399InTxT3/Fy76DozB0+IA?= =?us-ascii?Q?7JhbEnHxrI6gHEwX9sTwpm4WQeZK+1zrEIYZveXH8EPWwqhGowNmTFlCS2du?= =?us-ascii?Q?5g2mg3EjkaXUrqu2YsVaZVBxAvZ+t4ZnUCqzLE7KA2FANLltKI13t4ka5pWo?= =?us-ascii?Q?KWt6X9Rziq0FWNGcYVYfpraIk0Z7F3XED75n0FefjcFvF98jzvPI5dY+KuFG?= =?us-ascii?Q?SpdHoOQerv3LXkCMjBT7svaQF2VUE7U1R1HyPpACIXLx4erNc9tMwTvZ9I9s?= =?us-ascii?Q?93625qWnVlf3JCpwqeRXqAQOqOC2UsJPr5pYoSEt4Ku2C611s706vkBPX3Lg?= =?us-ascii?Q?uEOCuv8O379tQoDsUOufWeJaGmvUflbDGSWvy7BroDDoxjoEoEx1tuF+hDPz?= =?us-ascii?Q?1KjwRY1filntCPYJadenQlf+i/c9hptjcpDDYanGYdcNFcJXoO5LlwLJ9p9s?= =?us-ascii?Q?YyImjUEu6UB/T9xM6KZZktuWtNJjzksWvZYdv6UZP+WmSCJKRZ9mmO/jdIXM?= =?us-ascii?Q?HguNjgCjF+jlcCLiI8Nc7Pipq24/oc5sR5PpWL/LHfkahdA9?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9ca0fce6-a8c7-4a9b-bdb5-08df06ad8c1b X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Aug 2026 15:44:16.1241 (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: sa1RCFUONUn8ueW5BplH3GM8C3H/4+mcRSmJQtT1PQDe3KcHE9Hl5LhC0Fwl5ktT8yKAb0JXUjqEu5TjISI+iw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8223 On Fri, Aug 28, 2026 at 08:45:27AM +0000, Eric Dumazet wrote: > When removing a source filter whose count reaches zero, ip6_mc_del1_src() > unlinks psf from pmc->mca_sources. If the filter was previously active, > the code moved psf directly into pmc->mca_tomb by updating psf->sf_next. > > Because pmc->mca_sources is traversed locklessly under RCU (e.g. by > ipv6_chk_mcast_addr()), mutating psf->sf_next before a grace period > elapses diverts concurrent readers to the tombstone list. Consequently, > readers miss remaining active sources in pmc->mca_sources and improperly > examine deleted tombstone entries. > > Fix this by allocating a new tombstone node for pmc->mca_tomb (as done > in sf_setstate()) and retiring the original psf via kfree_rcu(). > > Fixes: 4b200e398953 ("mld: convert ip6_sf_list to RCU") > Signed-off-by: Eric Dumazet > Cc: Taehee Yoo Reviewed-by: Ido Schimmel