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Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Kuniyuki Iwashima , David Ahern , netdev@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH v2 net 3/3] ipv4: igmp: Fix potential memory leaks in igmp_mod_timer() and igmp_stop_timer() Message-ID: <20260706153005.GC410724@shredder> References: <20260705181756.963063-1-edumazet@google.com> <20260705181756.963063-4-edumazet@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260705181756.963063-4-edumazet@google.com> X-ClientProxiedBy: TL2P290CA0006.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:2::6) To SA3PR12MB7901.namprd12.prod.outlook.com (2603:10b6:806:306::12) 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: SA3PR12MB7901:EE_|SA0PR12MB7074:EE_ X-MS-Office365-Filtering-Correlation-Id: 80af3e91-f032-480a-e41a-08dedb737b6d X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|23010399003|366016|18002099003|22082099003|4143699003|11063799006|56012099006|6133799003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?JTtQ/jBt9b9LaLWcAtxAOR5rceGwTRHYT3NrBNerVZTCngnirVV/XUnvezEo?= =?us-ascii?Q?Y+23omGoD2LwF//alHmQzinkEYBDTg+q+CvWNYVhU4ClQgWyk1H2M5DhPUpJ?= =?us-ascii?Q?k7yrA0vEck1albPVBGV0OC6Gcg76p6z8LpKG2lAv+PK44Ja1rvnGteRkUtxW?= =?us-ascii?Q?YOTd5ltqJkyRtjnblYRF5wBydqLJq1clRkWhkdyChUZJKa4hPqKub1TZxFWp?= =?us-ascii?Q?ABG+M9EUHVhdI2QbykTGJ6XI5lk+SIBs22dDCivbyE5/yTMLNU6xE5+x+7CZ?= =?us-ascii?Q?F29ZaMQnOLo6JOImL27KVfr5MYkV8blgYusn61kP2BkWeAataONF/hDcTZdJ?= =?us-ascii?Q?f5mnoYARjodcjsXeuhzEqiDQI2D5mzY94sGSaZ7jzyc4bHLIvTbWaJJmFX0w?= =?us-ascii?Q?qnBlVAHCI3T332pC17+aFuFF5bD7JMgvCIpJ7UWwbkG6REFTo1abPT4ublOB?= =?us-ascii?Q?7N14YEWpU45jImdZErzBlVPjzJUePlWIXIseKEfZat0jC4cIYW0FHKh5440I?= =?us-ascii?Q?libZxOk5CHNKtlcQkiybp3zbylqAKpb+r1wBcgmc/v45sYd51tzAEXsH8QuR?= =?us-ascii?Q?rU95lA/tdXJH+WlTgR0RCBloKS3V7drSxjjR28WfdEjEZ6YFxF/YBUC3kKcS?= =?us-ascii?Q?pV3ctsrPvZWBnt5TDCDs97uq23n/UJQVfpLJabjsmO1/TO4n2MOAQofj3Ypc?= =?us-ascii?Q?CnTbskycv1imnPDJyZFVaVdr+8GUKBSrwfPFLRxqam67jfKd7sdbz3Sc6ahn?= =?us-ascii?Q?QDlzC4f5WV1/Osz/n/cClK0wLlnXS9URQ0OQ9avFoUq7c2KFAW/srs6NOIjz?= =?us-ascii?Q?HKFNUjA9aJsb9OpozPTtWDnbbEg7pLMM8Ow667KxYcDirlLjqWfXVD8Hw4JY?= =?us-ascii?Q?V/NFD+9BPnV4g6tZPca26jq8u8f9Z81B4Ed/i7Z54MNQMiOiAMW7LidymOvv?= =?us-ascii?Q?HR8AefJ2UWBKLNjLnWlcQYvcjig/2eqkj6N72QHkCnHY1dnYAeUAGJzkX/nc?= =?us-ascii?Q?zNRUdkPTyR6+wxlw/ALfvcDwiQ1qMBxlFjvAvCorqTI/a815jfvlp4NyOWG1?= =?us-ascii?Q?720c01yNDwAgUzKVEFbHlQxHP+s7+VpqatSVynnGLLpV5eJPfEO1QiTVAgh0?= =?us-ascii?Q?qp6VgF//cWCP8c2i8IjKQuVU8qUFg1Jsc88q75hisvVk2C0xZGbeMYSqdqbA?= =?us-ascii?Q?O9RpQNG0hM00LoutywBYPr8Pkoya+wYoX3ZtVanG6tdJ/oYpI1QgYUOG1vVn?= =?us-ascii?Q?fNpE/8UKRf3yrcgQmEwMeSzBaLgxjacyEMfbZ11/EYS5znty5vuyi94h170r?= =?us-ascii?Q?/et49G3hSaqBWUdldZ/d3/SERgSZJjyQfmXFKdxtRaA4F8FXbildeTw0WWqV?= =?us-ascii?Q?koLnMd/ijunISdhyLZbqiGKI8jD3tc7t9CmmTqt06SQjKJoRpEwPAMbUukl+?= =?us-ascii?Q?xSdVDueJXU4Tr7/DGz1eBYwCYrOitWHa8uujH42O4wOLBFLKIG/h8YzUEoP/?= =?us-ascii?Q?yqVXG9IM8i3tve/1YgMLfp8XlNsn5dR+4mQ5+z8xDx2sP3dwmTdKisw9GaBG?= =?us-ascii?Q?/EGrbQZ4cm3ZlAJ3ZAIb0fE40pGfQThFMl/3LNhyNstszB7nSSb83w+HlAEv?= =?us-ascii?Q?rKQuRQ3DAFhvKetbAKs2zGaP6kfTMklrQFpdnt/WQAL4+SkLs/Rd//gs59K6?= =?us-ascii?Q?HjYbvz5/7gGNajWDPiOiO2Qo7aOeyI8D/sYNNZYN3/NpiADda9b3dZ8RXeWt?= =?us-ascii?Q?vnGzGhZ9YQ=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 80af3e91-f032-480a-e41a-08dedb737b6d X-MS-Exchange-CrossTenant-AuthSource: SA3PR12MB7901.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jul 2026 15:30:17.3032 (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: 2YAXFSZsE+VOnYbw7tasStnNN8akQ/Q8iwQLJkjdvoWMfjDUXH1QNGEnCTj/v485mWrGocQFggmf1BsXT/ZPyg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA0PR12MB7074 On Sun, Jul 05, 2026 at 06:17:56PM +0000, Eric Dumazet wrote: > When a timer is deleted and not re-armed in igmp_mod_timer(), or stopped > in igmp_stop_timer(), the code currently decrements the reference counter > of the multicast list entry @im using refcount_dec(&im->refcnt). > > However, both functions can be called from the RCU reader path: > - igmp_mod_timer() via igmp_heard_query() -> for_each_pmc_rcu() > - igmp_stop_timer() via igmp_rcv() -> igmp_heard_report() > > If the group im was concurrently removed from the list by ip_mc_dec_group(), > its reference count might have already been decremented to 1. > > In this case, timer_delete() succeeds, and refcount_dec() decrements > the refcount from 1 to 0. Since refcount_dec() does not free the object > when it hits 0 (unlike ip_ma_put()), the im structure is leaked. > > Fix this by using ip_ma_put(im) instead of refcount_dec(&im->refcnt), > and deferring the put until after the spinlock is released. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel