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Miller" , Jakub Kicinski , Paolo Abeni , David Ahern , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Shuangpeng Bai , Davide Caratti Subject: Re: [PATCH net] ip6_gre: check tunnel info before xmit in ip6gre_tunnel_xmit Message-ID: <20260830104705.GA2834418@shredder> References: <20260828103731.1951815-1-edumazet@google.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828103731.1951815-1-edumazet@google.com> X-ClientProxiedBy: FR4P281CA0166.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:b7::17) 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_|SA3PR12MB699018:EE_ X-MS-Office365-Filtering-Correlation-Id: eec04efe-ce86-446f-81a9-08df06840d23 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016|23010399003|10067099003|11063799006|56012099006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?6TGjvSiq8HSoqpQg78C5ORYgkWNtMSiFfvq/eyG2PX1W+yIhL3zxjN3/RxCj?= =?us-ascii?Q?dx56cPV6fD8hF2gLcr7TGYZfBzqAwtbDGxiWyGgrj9eLLf2FCyReoR9YRKKZ?= =?us-ascii?Q?zG6mghzSXvZ4v6IiDX+u6/o8xr7Q13Eo8dvqtvXQlGt1dG1vUkEwzkS5yDQv?= =?us-ascii?Q?VbYrNbOL1FIEm0ZQKQPEikaXjxaaIeyqeP0Jt1mdjBNg8lLVp8NucQyjmuan?= =?us-ascii?Q?Z5dEij6cyDcZgYRSy49IkVVl5Tr04d8H5Bn1ezw7nUP8aIm/rmSbcv0jmvN/?= =?us-ascii?Q?fC6iYos/1nyreQXnT7Y8vOI8VBlQFGVk+zWdzv7CDkMqbHc3iZYAbVFhW4fv?= =?us-ascii?Q?68zcp1BVarog4PCVk0jV+3cuJs2DmYp8zPyZqipibtA9eUkPD1eEWZ4FdX9b?= =?us-ascii?Q?H9m99riVj3dN7rhFg3JQoReS0ZUqlgLo11SgZn+Ry3mHucwUSBwn1jbXW5Tb?= =?us-ascii?Q?nsxzLJNyYFcbQA+P4rBHCa+sEqOCsA7Af43LdQYDBOPgUH93UbXM+l5n656u?= =?us-ascii?Q?vR/oxGNe9RQTPpnWE1lZZCif32yjYwhyE62IYdkr3CBFQzkfjWuAnjE07MGM?= =?us-ascii?Q?Cb7MqRf6rk8e7ULjx1g/Y9TIUcRHdp4oLrRhQUg3YqwI8qEYjhXJKY6NSack?= =?us-ascii?Q?h40qCipWReiZq7xc01T9MECmbVjcfG35AMry+ED+6nULZ48qONNQTd+eGt0T?= =?us-ascii?Q?0874RPcKLQRChTSBp7mrsZi6qUistALnVMu4aRQvGZEiGHaZvPmhjneXtykL?= =?us-ascii?Q?yRuk28S9NGEGxNPyiIscYNh8n+p0GiMWc+rHXw+kXjp+8GkKoIEyNcRNNl+4?= =?us-ascii?Q?XS5+2eQU8WGPKFwdTNtKC3R/XUdkZAX6MmNJYhfvQR0+uh5HZXcBjTntDm+o?= =?us-ascii?Q?Lb6HNFwa8iWqQI1cpeLymJ7ImykN08JR5pF0medtbERhE5JNcU/QmBPL+eoK?= =?us-ascii?Q?HdXb5KKYlAUucfnqdE+t5N3yVG/E0m1x6UX1UevIHF70CYVpHRwgSyqOc/3d?= =?us-ascii?Q?uZbMUhCns5CmTowlLuI/QnRzEFnogBxZnaPIeEzqc9e765onPafZZnymmyb3?= =?us-ascii?Q?8o8b/y7cYjY+owQyIFFnvhZlWE+B82GadJyW/qR23JHI5j30dKUnPQ6QCPis?= =?us-ascii?Q?SMHV70Pa49nxviSHOX+sZoANx5wUifpQtCi4fanrXrQ5+PyekUvN4xkyLvb6?= =?us-ascii?Q?zhdf3FmCrnnY0ISB3/GUFqpegC0LwvOHp/E/S5JL4yR+VNB3JyTPEmHTRB2O?= =?us-ascii?Q?tcqsXMGcaPYBoJpJl2KeCcE2zZqbcxP4IOrhf66XyYo/+oh2W13/jsU1PAaZ?= =?us-ascii?Q?ySuJrU5g7e38nT4suPuNh/ljkKGre9Y6SQCn++0GlQkyYNPK65dgnk+o6QBG?= =?us-ascii?Q?2pebwZoyrQyCHY2Wd92XyukpUljh/sXrEkUUUa0G3e++5MIbHZPEkY3eqOJA?= =?us-ascii?Q?WbBOowqfGGdBNTCdQxwnafcmCCTPKTFeVYCjBVjQz7qhevpO5KUFuwkpG9sj?= =?us-ascii?Q?YqGS819cgX5swDE+qBdiFMlB/ZjkQqDgeqW5nR1OJXqc1d7M2T5NosJhey6g?= =?us-ascii?Q?a1iiKQ0tHbLKEy3uzUuUahg3xjWv1AH5lN1yvk9IkSD0mEh9dPOM6dAvpSMf?= =?us-ascii?Q?jcilOZGO71gYTTKPflfOlCRpkPExWyvlz3LJnbEx80qR+bqcbohaJj2sxvaC?= =?us-ascii?Q?OnH7dnzOhSNawq+3e5rS6827wtHyOF7bGyPeH3YFzdjKp7HR?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: eec04efe-ce86-446f-81a9-08df06840d23 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Aug 2026 10:47:13.8916 (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: ZQjgEBFb6Mklzcynh8CKtut2aT1use1gF0U/Ql7JE30yBMJvU125ELUUxKsrDecCNcjvDYWHWRLmz0cV7Ved1w== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB699018 On Fri, Aug 28, 2026 at 10:37:31AM +0000, Eric Dumazet wrote: > Shuangpeng Bai reported a KASAN slab-use-after-free in > ip6gre_tunnel_xmit(). > > The precise KASAN bug was caused by ip6_tnl_xmit() consuming the > skb during headroom expansion and returning an error, while > ip6gre_tunnel_xmit() still held the stale pointer and called > skb_tunnel_info_txcheck(skb) at tx_err. That specific bug was fixed by > commit 87f21b59ddc6 ("ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()"). > > However, calling skb_tunnel_info_txcheck(skb) at the tx_err label > after the transmission attempt remains problematic: > > Downstream helpers like ip6_tnl_xmit() call skb_scrub_packet(), > which drops the skb's metadata_dst before transmission. If an error > occurs later during transmit, inspecting skb at tx_err sees a scrubbed > dst and misclassifies tx_errors vs tx_dropped. > > Commit e5f7e211b6aa ("ip6gre: avoid tx_error when sending MLD/DAD on > external tunnels") already handled this correctly in > ip6erspan_tunnel_xmit() by checking and caching tun_info before > transmit. > > Align ip6gre_tunnel_xmit() with ip6erspan_tunnel_xmit() by caching > tun_info before xmit and checking it at tx_err. > > Fixes: e5f7e211b6aa ("ip6gre: avoid tx_error when sending MLD/DAD on external tunnels") > Reported-by: Shuangpeng Bai > Closes: https://lore.kernel.org/netdev/20260819062224.3197349-1-shuangpeng.kernel@gmail.com/ > Cc: Davide Caratti > Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel