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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , William Tu , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2] ip6_gre: remove obsolete ERSPAN PMTU update Message-ID: <20261004072707.GA72754@shredder> References: <20261002033058.358137-1-4ncienth@gmail.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261002033058.358137-1-4ncienth@gmail.com> X-ClientProxiedBy: TL0P290CA0001.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:5::15) 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_|MN0PR12MB5762:EE_ X-MS-Office365-Filtering-Correlation-Id: da36fe42-8b19-40e8-43b1-08df21e8eb2e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|7416014|1800799024|366016|376014|10067099003|56012099006|6133799003|3023799007|11063799006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?Uk7CB0mr3sXwtBmcTSamYW85ZkJcVADrQTEGDiCsKZoMFk85PfNBG1BJ4LWy?= =?us-ascii?Q?XxJNl/WPUrnVea928LlEXoQ71B5f3tZMDHpuUNuPmCdZlrj8nmKX3Ls8D8ZS?= =?us-ascii?Q?y/tTqiOtMUX8WdMmvl632ZGBIwhBc95maDe/uJZtB0uXxbCCTMj2yO7kpwbB?= =?us-ascii?Q?UgAG3LyYcZbihcjh4Gpir57oBYOKL/xWYsA7HltwbhqiioF8kKIhW+w5DIDK?= =?us-ascii?Q?6Itb7S9xXhd2Fy0OPu8xizCNomPkYMFzVI4DTrQvudWOBlhRNtnJze4mM4kJ?= =?us-ascii?Q?s/gzrLabpzyGP1oA+cxafv+GlDpxJo6HLfK6kKuxeqwgKQacCk3l7axUD/W5?= =?us-ascii?Q?yhIAYtm7uUCEj7qgj3B8Vu/OIjEHB2zKLpW+rSaXn9j720iMc4Z60U+BUW/Z?= =?us-ascii?Q?CxPwr8+v8jLcUJTN0Bvk5rC80gR+acMqcMUVVGdtMaBYKWUo3/j8BviVd76A?= =?us-ascii?Q?1RHi0psrtGsMSFaylGFQcdGbDGFU12uT/Y2617V/mmCwKQrY5YQSVOrAT3IW?= =?us-ascii?Q?D8I5xyErSOJh61w5TltE8twZgpmTqvvdGqt/BoVDbDhMYvwSSceMLTQ5DwEQ?= =?us-ascii?Q?Bm9l3EG/Xuh2Z8ULPmGfyISqyI+SirFrPW+iI8aKK8PuBu2Gm8heMwV8tHfe?= =?us-ascii?Q?X/BaR68+Vls6jPROOminZitxyi78ATw7Ayr/gigFHAjqBfXe6jCptCFi9q2E?= =?us-ascii?Q?viZdm83wBdACu64/rOvPjYS0N4fVszTLQwylYpHH9Gcxx8YzYSpZ9NuVOx0i?= =?us-ascii?Q?YR9YqQsPWSISUywvIcdbm4RchBRUwVDXNyFpeS6DPE14uQJYw89RSQOoXKfK?= =?us-ascii?Q?j5cFAdltPMeQdpYI/HhJ8sKvjMtTayIqrPE/5EjB7TfEm0Lmr17CQWxsRPKj?= =?us-ascii?Q?6seH9CWQEavP3YH1ZPvAjOBrjBrQv6yvV642gQFC0kPjaWe2i8IplTgdKwiY?= =?us-ascii?Q?VtVKMC6/GGLiLILvCQxnP8V9xcVRlvbqrMQ8qUW8NDMhk4bV7lWASSDbYdDA?= =?us-ascii?Q?o17e+chu1Om6fTLDM4ZMtoYiTxnhO03BYMecHmbpkbv+RcTZkK8NksZRw0oM?= =?us-ascii?Q?tTomYZaBM7cJWf3zaS5t50ZwFvUyGTYnIHZtpBRlhWXOPDnBaxHgTaClep/G?= =?us-ascii?Q?rJ4iw4bKCxhmiY8hZWJppC2LRe4uiIJbGiMDLlYeqTqUXQwF8taxSCzV5tpe?= =?us-ascii?Q?37/LV412HNYp30MsVgesFLu3jwOfl1BdrnxcV4XFExkuAoBQzJgdaY371Yol?= =?us-ascii?Q?HrZtyr9w83D4gqo4zYvlT5cNPrG4TZ/ajNOEglGAS6t1s0gyZXwOONhPjqcm?= =?us-ascii?Q?4pP/jBR/hsUEnBklbmeT23oocTXdLdHDc4ERK3lYOrSGFTlhIUYLDrzLfKAy?= =?us-ascii?Q?wS3knV2a1JC0jTYHKAy7OfA0RjAJW8+4NffR5371lBSTtSVSXJ7j2VSkc9Tz?= =?us-ascii?Q?lwfIgbDe82oppwCRmGU3PogvfgN0ORXvrvlYNIhXup6yh0c0dYTPcG6KxNdb?= =?us-ascii?Q?f6yf0RrmB5AjOIdEtROeTOQRyWAOzBSN6cgvotZO+ZMKAApNcKUSTCL1XV2q?= =?us-ascii?Q?IJI+7+x8EH3qYag2bhqLqOkc9E9Ut4xzbXq5FzeZVMMDhx7OprjkCePDkLVX?= =?us-ascii?Q?mK8a4KgQ4SgvZckwiwtP6J+OpwG3cMECnOEE5FoVKQ6PnkpJcSBQjzs+/ZuN?= =?us-ascii?Q?IYPv3rPPqgbRp70i4+LRH2Cr8I0ph4BYl8GimrhpsJ3CQU1e?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: da36fe42-8b19-40e8-43b1-08df21e8eb2e X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Oct 2026 07:27:17.2733 (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: g3JX/0ewCA6w532daAOChY8OwpjgHQf5TpwW9f5qHKiqS2qaC3VAY6kBJ6L1XiuHoAFFzdTIQAFl4HmHF1KtlQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5762 On Fri, Oct 02, 2026 at 12:30:58PM +0900, Daehyeon Ko wrote: > A tc tunnel_key action can attach a METADATA_IP_TUNNEL dst to an skb, > and mirred can redirect it to a native ip6erspan device. The legacy PMTU > update in ip6erspan_tunnel_xmit() treats that metadata dst as a route. > Since it has no output device, dst_dev(dst)->mtu dereferences NULL. > > On v7.2 with KASAN, an initial UID/GID 65534 process with CapEff 0 used > self-created user and network namespaces to trigger: > > KASAN: null-ptr-deref > RIP: ip6erspan_tunnel_xmit+0x10fc/0x2cc0 > Kernel panic - not syncing: Fatal exception in interrupt > > The update is obsolete. Commit fe1a4ca0a2b7 ("ip6_gre: process toobig > in a better way") changed IPv6 GRE Too Big handling to update the > underlay route and removed the equivalent block from __gre6_xmit(). > ip6_tnl_xmit() then propagates the underlay PMTU to the overlay route. > > Remove the stale ERSPAN copy and its now-unused dst variable. This > eliminates the metadata-dst dereference and keeps ERSPAN aligned with > IPv6 GRE PMTU handling. > > Fixes: 5a963eb61b7c ("ip6_gre: Add ERSPAN native tunnel support") > Cc: stable@vger.kernel.org > Suggested-by: Ido Schimmel > Assisted-by: LLM > Signed-off-by: Daehyeon Ko <4ncienth@gmail.com> Reviewed-by: Ido Schimmel