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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?QkKdsWafkOOHXzyIgQj7dqgMRD3EUtrlNMTQafEgY+j8+BqPSMZLLUzrFZQG?= =?us-ascii?Q?qI6uRcv2AcYHNep/vcJ+3FsWeoAN2HMw8TUeXnlCymrEZEMm8SxLOjWUnW0D?= =?us-ascii?Q?s1fvJfhApdV/IR6SBAbIfG69y+IQJZVW9qB1LX8A/DhzzGhWLDKkAqZhAZRg?= =?us-ascii?Q?a/qV3AKBSIfiHj5XPF3CKGWEvg0mqxgFT3H62UM1/w6F1Y8ScBBkdUR+F2O1?= =?us-ascii?Q?vo6WLgBIvFM2qk57LHr9wbtTMn+1QHw2qlzcd+vTKSG3uqqfxIXJf4eFJGXu?= =?us-ascii?Q?qXRq36AJdeB2e8sxf4CGb1J8NmjmhZpIJLahh2c/EXliZhYFju7Srn5bug0j?= =?us-ascii?Q?0q+9s7j4K1Dr6Jycfr9IhggWEHTt/bagzJqWQa67aIxRSRxj24G2whvs6giz?= =?us-ascii?Q?YdarCBN5j4qhRlE5wlA2g2522RbFhiHkwilwFI5mT1hct2pkUZ7mCfxwlH99?= =?us-ascii?Q?srnucmcwm+a9jAcmV69REmU9W4IE4CV+6PUiF9RUqJyQYwvlgwDKykDPuR8o?= =?us-ascii?Q?NovNmr6807+P/ACDkoClqtfooyHs2e/FU+xBSJmI5mjzPpvMqpKGmwLe4cOR?= =?us-ascii?Q?DCSTfV8GlWSXDtyBPj4qJYSUkL11UDP9UxkLLanfogl0iXYiW+yz6fsrfla4?= =?us-ascii?Q?pks6DJ/sbbd8G19OKYnShzpIA6ZAnWnjhW418LRqRCsQ9Pyb3MdcjfD08k2b?= =?us-ascii?Q?xgG7Lm+4xRu8cICt3ej/VYAnrVNaTgoE/4mKngWilI4Jdbl2+N0n4JofKVre?= =?us-ascii?Q?mjdFGidGUeZFSG96Q1EfKWyg6vZi2TkoI54RsDjBMT9tNXcdq8OJeEeudGQY?= =?us-ascii?Q?11h6nqSwqDIdWFIvqdyJXKZjIg9jQLKChZUpJGHRUxul9K2MOn4I18HBI9hS?= =?us-ascii?Q?74L3H9Yd9idUMBa8486hHnOtbmDb6dGUAmu/U1ShfSyMViNOzTMH7CuxHHR5?= =?us-ascii?Q?7ClZw4InKDL2D6Eh/zckGCUVMNIkfgCbXRVl46tDK37zE2lupO4SEW1nXl9q?= =?us-ascii?Q?2X08YKq65C/4EgZm9EHG5oOhzIpnzlYJOJXHCP5Kl3TUhY+ceUmeZVrC3ijw?= =?us-ascii?Q?CshXNwYugZYWIZt5Perr93UeUkFw34cf1kdmP/L0yTaezdK7Dbj6Dfjy54jE?= =?us-ascii?Q?qPSrqYHIGNSl1Ngb58nbrFbQE/AgspRUx02CXOuvVBjVrJ3WQTygPaFt0Ukj?= =?us-ascii?Q?6ZeZZ+mll+PgmxYGXx7guTqxE5Kdpg1j/bfumwiN0KyqHdSZJGiWDrixHxoU?= =?us-ascii?Q?cpLx2ViWgaq9g+JfknfIVlzY9IknvWuk+OPAn22Q81O4asjKke953MaUXy7w?= =?us-ascii?Q?s4aREJjRdVAwmJDLiKPBNwLnQjf+ztvS9r857qrINmZJ9Ck4J0sTV4Agifxg?= =?us-ascii?Q?PXME2rOdSnqlrVA0A7ITTfLPFQ/qzS5da2zuhgnt1CcelKB4LzFfau5gcJQD?= =?us-ascii?Q?wUDgNbgxJsHkNvCxR5qp+TTz5FwGBmQuIZ3yEJi8D/0KmuDwwCitUrd/u1UW?= =?us-ascii?Q?ubAMwX5s/fYCLSXzJWlpsZm4lw6UyrS1A+f2aoROUMBAdA7xfWAV8XUDkGmk?= =?us-ascii?Q?ySWAxHlqKJJnbur0KNB6CHPn8D0ls8Tbad2Le7JVzPiwk9vJtvgDGKbtwOC6?= =?us-ascii?Q?OigrbfIzPOEcTREhyLHTestAgbTXz9/CzVdK1pEySlEjU/Q1RarCnHmgXCx5?= =?us-ascii?Q?nYDjeNDtdp6PjGo1b3HcA11d+mQerPjxH5ODXw7DXYoJLVn1?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: f7c94fe9-782d-4d6a-c209-08df3698cbaa X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Oct 2026 15:16:39.2935 (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: Lx5JvK/o2bOXnAeyrsC0cTNPhOMtbHVLmO5C5KTN3Uea3ZPg2DKYvK/9zb+669ctP46tQTUI/fNuoINDbNAjfw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA3PR12MB062244 On Wed, Oct 28, 2026 at 07:57:10PM +0800, Xia Yan wrote: > ip6gre_changelink_common() calls ip6gre_tunnel_locate(), which only > looks for ARPHRD_IP6GRE devices. The same changelink helper also handles > ip6gretap and ip6erspan devices. > > This lets an L2 tunnel change its parameters to match another L2 tunnel, > since the duplicate check looks for an L3 device instead. Incoming > packets can then be delivered to the wrong interface. An L3 tunnel with > matching parameters can also make a valid L2 update fail with EEXIST. > > Use ip6gre_tunnel_find() with dev->type, as the newlink paths do. > > Found while comparing the duplicate checks in newlink and changelink. > Confirmed with ip link commands. For example, with an IPv6 underlay > named under already configured: > > ip link add tap1 type ip6gretap local fd26:106::1 \ > remote fd26:106::2 key 100 dev under > ip link add tap2 type ip6gretap local fd26:106::1 \ > remote fd26:106::2 key 200 dev under > ip link set tap1 up > ip link set tap2 up > ip link set tap2 type ip6gretap key 100 > > Before the fix, the last command succeeds and received frames move from > tap1 to tap2. After the fix, it fails with EEXIST and tap2 is unchanged. > > Tested with standalone namespace tests in UML, with three runs each for > ip6gretap and ip6erspan, and with L3 GRE IPv4/IPv6 traffic and normal > tunnel updates. Full x86_64 W=1 builds with adjusted configurations > completed before and after with no new diagnostics. > > Fixes: c12b395a4664 ("gre: Support GRE over IPv6") > Cc: stable@vger.kernel.org > Signed-off-by: Xia Yan Diff looks OK, but this is not a regression [1][2][3]. Broken since 2012 and nobody complained. Please remove the Fixes and stable tags and target net-next when it re-opens [4]. [1] https://lore.kernel.org/netdev/CAHk-=wiSnTE9vBZ=5_v+3EEkdazCCbBM5YABRzRHUAeRdyd4Xw@mail.gmail.com/ [2] https://lkml.org/lkml/2018/6/24/113 [3] https://lwn.net/Articles/1074171/ [4] https://netdev.bots.linux.dev/net-next.html