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Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Qiliang Yuan , Kuniyuki Iwashima , David Ahern , netdev@vger.kernel.org Subject: Re: [PATCH net] ipv6: account route exceptions to the netns of their dst Message-ID: <20261018152533.GA2597316@shredder> References: <20261016091556.2750902-1-edumazet@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261016091556.2750902-1-edumazet@kernel.org> X-ClientProxiedBy: TL2P290CA0009.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:2::10) 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_|IA0PPF95ABFC125:EE_ X-MS-Office365-Filtering-Correlation-Id: 211730b8-879a-4c5a-c7ec-08df2d2c12c9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|1800799024|23010399003|366016|56012099006|11063799006|10067099003|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Mrh0MBowf+3WF9P8ZN3CbNpZ4umtNr13TgKtW0I7vRJTgDLFaGqd/Khw68Pb?= =?us-ascii?Q?/9vV8fT3LV1S2iJ7HbyNnKufxcTNZs4bCLC3bFxnGHExpfPpNAVOws07TxJ2?= =?us-ascii?Q?MoEomnx24yoxgyCxsuYl/Rko2t/cBf3sFeIhf8yYfK8y63vWTBVCd9mInUC2?= =?us-ascii?Q?F4dQXJOkkH7168Pp4pynDgSN9kD2I+7HSSwGveEZLb2HWC9uSEMKhBUNkN64?= =?us-ascii?Q?EB7ZQQCGjMsfQtqmUjmm84kQCNSQAchp+wVqM0Y/tLKC4mSAAJBedag7fDkp?= =?us-ascii?Q?eEJGG69DEDJvTyv0GFzCmzANH07xniuhaQ3FLELUeU/wo3XzOuj16gbqZQ+f?= =?us-ascii?Q?lij4snryOLERtzPg3NyfAYr5hLF3v4xaaDR6UCWzusIKsB76ED0OAJjzIjg8?= =?us-ascii?Q?K+AIewjU3Bg1hs29YVm9NappMJvcvw9djL/wXfptnpSVZxxad89zB6QkDvxR?= =?us-ascii?Q?uGlDOOIaN0C6A6D3kCLr5+gr8oK1zeHEMQd+qvwwj8LQXXEOcKRuKR29fzCX?= =?us-ascii?Q?bA5dPLQbYz7EyDjJA9OYKawn6khtAfudeFhdlbdiLErF0jIMfUZ4JzkvKMq5?= =?us-ascii?Q?wj/QpnipnuXhL/NXDeYbBasiBbYqszT6WtKzO6RMZSj6HHgmZgFKZ830Mh2n?= =?us-ascii?Q?hge47QZfY7FU0yDTaY7yJwOIu2FQT7NchRdwcCnG3rAdUPoIIklBjowZvuw4?= =?us-ascii?Q?yLWR5HD4ZC2xv7pLD+DTYG/A5NC/c/6uZnwFvgLYnhXxmSZEhzd1Ad+9Q3rJ?= =?us-ascii?Q?DouAZwbIJ2iVcCEBseQVoATKrpwG5USM6tK+Nu8ibiilPJTkOABP6v3TBJfF?= =?us-ascii?Q?vmMV5QPcyfIapseuh8kfdBmnp9cUoan/xGV6u7Ka++53NjMzYn9fhRcewKbt?= =?us-ascii?Q?cMg1FLfrEd/9+8NxP+6LTs+XlRBfa6eXCEmba6gX/SByVGKFdWqk3uz8ivAW?= =?us-ascii?Q?PKazWCOXjv6QXpL6Kszi8EpOMQUVMaKFnpZM/WKtpf/BLa8LXnOMYiC6UQGF?= =?us-ascii?Q?PXbpmoAEUY4ETZyLimoOWxp4QtqNSUCeoYft/rvZRdMzwVg+ijBO9kWx+Vho?= =?us-ascii?Q?iG4RhImEdlFSvF0b5OMCPA83gFwhOmB2capXmaY0zLXL8scEQL0lDo4xQWXG?= =?us-ascii?Q?UOxI3KK85wB5hALSITzvcIZoZfKHOBdMdLC7SBii1pxSJOJ/CNBWWqAvEt7G?= =?us-ascii?Q?+wxRsUe+/Eyb1BppaLWv+8bPYelPloGSKzMALBglXVn0RJco0N+U4s4x9+MN?= =?us-ascii?Q?D7eoow2ACf2vrLpBt8wvzBq83/IT2vJpRiguRJ3FRZgcJ+7LR3VixyjskeC/?= =?us-ascii?Q?ZtJpBFEJ3GHSQpB7H3v/byjcx6h+dtTPkz2R/8JOmDo41JkLxm8pwzYGlDBv?= =?us-ascii?Q?+iAef0YtQuSGvnwH39/9uRHeJ+bHvbFb54mT0hEIyxccpBqks1nWKqMiGJcl?= =?us-ascii?Q?ibtYar6zgHDdfnT02sCAuK3Ed/aAlLVedgqAoFocwiSn6ogO5wViVyUhQZ4y?= =?us-ascii?Q?4fqT/nQIeYFPDCbwztNUhMPYmZlZ9slTLNY0cy/jgc1uNNzIwO8wtOlVTqD8?= =?us-ascii?Q?fMV/ws10zEvbypVRuBJK80TuE+w13R42hlzJ8zoJ95wrpeH5X+kQBHXT8GmO?= =?us-ascii?Q?FKKplX3ynXFjKU+PV1iewWMNe8GbcEE41acPjz+rgCjTBMxh8Fzd+gP1YjKW?= =?us-ascii?Q?q2XboD5jWwQ3Q/6CK4dgJSMVU32xJR7vRq3FhZF6guLXApoc?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 211730b8-879a-4c5a-c7ec-08df2d2c12c9 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Oct 2026 15:25:42.7854 (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: +4MXoUv7q1XruTDQo6MoMVfjzRsmuJEjGs4hz+SdEkYh5AvLArLn6G59dzFEjR4ZSWJnC3l7IzHBgGhUe6/uCA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PPF95ABFC125 On Fri, Oct 16, 2026 at 11:15:56AM +0200, Eric Dumazet wrote: > rt6_insert_exception() and rt6_remove_exception() update > rt6_stats->fib_rt_cache of dev_net(rt6i->dst.dev), but the device of an > exception dst can move to another netns while the exception is still in > its bucket. > > This happens when the bucket is flushed from an RCU callback, for > instance from nexthop_free_rcu() for the nh_info of a replaced nexthop, > whose exceptions still point to live routes. If the device moves to > another netns before that callback runs, the decrement hits the other > netns, whose u32 counter underflows in /proc/net/rt6_stats, while the > counter of the original netns never goes back down. > > Account exceptions to the netns their dst was allocated in, derived from > dst->ops as ip6_dst_gc() already does, which does not depend on the > device. The dst already relies on that netns' ip6_dst_ops being alive > when it is destroyed, which happens after the exception is removed. > > Fixes: 81eb8447daae ("ipv6: take care of rt6_stats") > Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel