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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Peter =?iso-8859-1?Q?N=F8rlund?= , stable@vger.kernel.org, Vega Subject: Re: [PATCH net v2 1/1] ipv4: avoid divide by zero in fib_rebalance Message-ID: <20260827193454.GA2320979@shredder> References: <20260827182514.4667-1-zihanx@nebusec.ai> <20260827182514.4667-2-zihanx@nebusec.ai> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260827182514.4667-2-zihanx@nebusec.ai> X-ClientProxiedBy: TLZP290CA0014.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:9::13) To PH0PR12MB7957.namprd12.prod.outlook.com (2603:10b6:510:281::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH0PR12MB7957:EE_|IA0PR12MB7674:EE_ X-MS-Office365-Filtering-Correlation-Id: fb13e689-8c06-4064-ba0f-08df04724a7e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|366016|23010399003|10067099003|11063799006|4143699003|56012099006|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?l4K0FT7rHP1YDZIOb+AN3R8wqrXzVHtO3uaUjUPdj9Cj79t2MqNrKXTf9emW?= =?us-ascii?Q?Ys+71oLcwexdkbdbdk0A8wQo2lObkdwwx01yvIGTD78Kl64Ugr6aC998Y+Bm?= =?us-ascii?Q?JjI5zT+IawvV8IYZD3zF24Ci+tG/rPG/8EZkgh/zZyg/X3pTzeQP9Ip2KxZN?= =?us-ascii?Q?Z8+kXY1Vax+rC7DGndeGpn0U5fV+jCxiBseCYFw23d5NvDUzZn12xyuCLcSV?= =?us-ascii?Q?WYDhqECU7nqntO2EF9I/G87E1KPdiPjWcQG5Xc1B9CyiHJA10gy+k6JaUiro?= =?us-ascii?Q?jcv26DzrlRfToN5v0MtpBu2Y7LpzpkAAGLkZW0IHhIJKW4WQdu0BZbptphUV?= =?us-ascii?Q?iSZZ2aP8LX5DEayhs977V7Wwwke+QPWazr0fcqmJnr+maTanhUvLLnKcu+uc?= =?us-ascii?Q?8MUi0CVliH9Ff5QmRHR9rdol4LlaAvHw/btL6y79JeHrJewikbh9Ju91zeaW?= =?us-ascii?Q?BsDfwdhnse6Xan4w/dBaWxPvGaL7Nx8Hh/pzdydRIEtpY8SlyyN7ZJgMXnX+?= =?us-ascii?Q?weSx9oRjrhNkFWhsoheQMRfusRyE0dHehcfplu8F1FF1UesAE78HKeO8vBZy?= =?us-ascii?Q?ELlP/slk7wumVwSyZzUc4Du0IeL3dOi/xNMvVykxD5AGjM+6gcfpyAysWfh3?= =?us-ascii?Q?jg1KPjcZpZyuBFG0R/17gQ/AV0dPAuyzZB6THNG+Escf1NUfJ6IR3nD1RNSb?= =?us-ascii?Q?TgVuDTWBXB8HVmLQD7AnUtR1ohEdiImI04Umbj4WZ6kJvgcve4ISkqiTASJ1?= =?us-ascii?Q?CW8KGoG5jSIBi8W07Y+Z41G0RX1y49liM23sutyazMzwYZ8psoWB9CJFrZTE?= =?us-ascii?Q?R+xkL2I3fK9KIwPS8M3F3npOdFwiBeqnGYLw2mrOzAik3v4femiMvyz37aeL?= =?us-ascii?Q?n7UcmVMiklPZeO82xrQs62JDhMnDHLNr5s6nq/lDH4dFWvMdrrYOVWDPDhfS?= =?us-ascii?Q?kF0LGIbB7LeiF5sx86PXLtnRExwGEhTQVGGW2P/65Ce/l/II7I+YpwuuGKs2?= =?us-ascii?Q?NdiVkRvnTPmhPd3A6NH8kH1useVJPiIlGF1Q5LzdoS7bjdbgPk6vFOh3BlIL?= =?us-ascii?Q?ZgzTFnIJMkDNgraJWj7aMxd1HPCpIRlyy/CM8oEoear3ZCEIXLxw6nXl9LPY?= =?us-ascii?Q?jXoIp+wOUp30KwJjJpFe65ezG2FnOa4UAs5Cl5XIepIVI00We2G+Ie95COvj?= =?us-ascii?Q?8gqNVLn69Qi5ctq/EoJ9CU26T5EzSNPki/T7wI8VRL37oiv0K/mzYIhYbYTE?= =?us-ascii?Q?0pVXXoSXyNLRnv8ob9UoHUkWWjDvMGaVkQXrSRigbaiQbn4D0NbQvreEDvk3?= =?us-ascii?Q?tuCh0cnV5+rlWJgkTaGklYL6+N22S1bw2oFQQ3CuiQW5EWRvcFTB02J6tkuz?= =?us-ascii?Q?Mwp/HpWpSptbXlN3PUaAPL5uaMsoH88mXZuDFWflFN7f6V9WrODZad/w3M0E?= =?us-ascii?Q?89BPxosXbQKKatwlERKUuPGqKgcESarIsAQ2HZQ9aJhyweVovedQA28ElsX5?= =?us-ascii?Q?aNlvl4Kt5D53imrRq2m7GmNAPJls2ma3wa8IxRT5+TIyDnAKoG3w7wdUnMJv?= =?us-ascii?Q?BSUPpZXXonSGAVeNvFgAbOIeSdCFg3v2rIJh9ZlPZOP1I72A3ZvcDSjI5hOg?= =?us-ascii?Q?24cq6JMDH3PFgy9vy3ESdxpQ4GpcV9hLI04yDBHgveliuudWVYPahS1niUYl?= =?us-ascii?Q?xH+ox8VuCLic9kauvebmaEVWx9Gsb7Z4HwlKvPSv96R8nPWYOAqkuCjM+uGw?= =?us-ascii?Q?+zS+BMIOTg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: fb13e689-8c06-4064-ba0f-08df04724a7e X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Aug 2026 19:35:03.7639 (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: ll/HJzEEvjfIC5Mg0EtWdwkIfY7tSjkkJPaDWoZMVr07K+1cNx7yTkuvOrPfcM7A+cbzlTMQwPNIOtm5AM1x6w== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7674 On Thu, Aug 27, 2026 at 06:25:14PM +0000, Zihan Xi wrote: > fib_rebalance() computes the total eligible nexthop weight in one pass > and programs upper bounds in a second pass. A concurrent change to > ignore_routes_with_linkdown can make the first pass return zero while > the second pass sees an eligible nexthop, resulting in division by zero. > > If the first pass reports a zero total, set each nexthop upper bound to > -1 and skip the division. This matches the IPv6 fix in commit > d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") > and preserves the lock-free rebalance path. > > Fixes: 0e884c78ee19 ("ipv4: L3 hash-based multipath") > Cc: stable@vger.kernel.org > Reported-by: Vega > Assisted-by: Codex:gpt-5.4 > Signed-off-by: Zihan Xi Reviewed-by: Ido Schimmel