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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Nikolay Aleksandrov , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, federico.kirschbaum@xbow.com Subject: Re: [PATCH net v2] vxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del() Message-ID: <20260827091744.GA2039952@shredder> References: <20260826173604.90158-1-baul.lee@xbow.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260826173604.90158-1-baul.lee@xbow.com> X-ClientProxiedBy: TLZP290CA0012.ISRP290.PROD.OUTLOOK.COM (2603:1096:950:9::10) 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_|IA1PR12MB7687:EE_ X-MS-Office365-Filtering-Correlation-Id: 23c0af89-fca1-4174-c2e8-08df041c12ed X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016|23010399003|5023799004|11063799006|10067099003|56012099006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?mpNZniCnK+W9kb+v4NbUttCZCAzwQPdDT5FNoAUFi2CGd+n8BWMt6a0kPnkf?= =?us-ascii?Q?1vPUdwgcxoMVCPH/9OvUv6P1Kx7oL1C2+W6xrtTOUv3dU+y1VxKhuyFT3a49?= =?us-ascii?Q?CONfXeuf1yAoJ6lH3yJK02Z0dUlx3jLO7+9eM0QXIzmUuitzSnERsWvQCB+1?= =?us-ascii?Q?1q2mG90fMD4yWedpYDrq4cOrT25rRh2N29YoXuOkny2lBilCr61d8AGtyHil?= =?us-ascii?Q?iisRpjLumuj9mLBtWJ3vYM1csm3oN8SytxCb+nhI7J+t8LbhBL0nG/Q/6nYH?= =?us-ascii?Q?I9QX14NV7QfWYOPga4KsFbj15L0XhXWS2KUpswExYgNSeOLK3vOIU0QlrCTn?= =?us-ascii?Q?g8aXvhLEj3zQDCBNYwA9I1vksm6dS5jN896/wcf0sjjAhpM9XGDcdG2PZv1g?= =?us-ascii?Q?0P2BDlcYvreze+6of2Jj30Bq+6BnP6fVFeDcxbgpVqWSnekxc5wow3NxON6v?= =?us-ascii?Q?2hh6E+KNK+JEQq5TFt7f9yILrUEnfpTRd70RHwK9UJG1sfXb12iX2QLrKD+w?= =?us-ascii?Q?eLvyyBBPdzSfe4WAUrHBpltSZERGQm/pxwHuB0Vb4+cN8Rp613BRZj9DkgI2?= =?us-ascii?Q?8Vc6OVhcSFwr4AuHLWQfyJOkbK3nI3GZ/FTVOVlODm69CXoflgXNX7rHrETc?= =?us-ascii?Q?eXUkVi4vixgRbquBs3c2MJdG+0rO5UBMlVxeHEj3UDfCbLBaD/wVYP5vrZuv?= =?us-ascii?Q?cZO4Srm7c9+bClisSjORbm815Xx5CUE1kHuKTPZqtQ4JOZYtIrvxSCNwmcgS?= =?us-ascii?Q?iym7d+j6U/cp+8bciU2S3b9qMV1Z6n43bhlVvmwC9JQp3KBU7fYPWD2MLc4K?= =?us-ascii?Q?gUMHNrWLe8/jDf7QQvfoNeXmhu1TkqcZMBEUuxh3xmgs4XaXiLsxXfq+D9KI?= =?us-ascii?Q?4vi9auZu0Rpy83s0NwDXHIOo+A3OKqpq14ApcujI8ezXh1y5/tgTVpz02QRz?= =?us-ascii?Q?V0O/qQgtNn2G5F7QkiaYSJ+i1wzeXeMbCL8GbhFWqNWsRVDabvHaYb59V56R?= =?us-ascii?Q?0/LwGJYW/0N34yjgikxCv6BZgmEb+eKzAI1s4G/Pkr1yL+krkCAlTCCEyI6z?= =?us-ascii?Q?aY4r/k8OnA1ZPrGj/wSFYJ5+SHoWZSQ3Vp7jXFelEnpTOLPJzZowWp/LdjfA?= =?us-ascii?Q?kb2WmZX2LJwNopBlIwqZuVrY7sWu/ZZTr1PZDC2C0ckRRi1HF/pq9kYmFoL/?= =?us-ascii?Q?c8CSCGLlytbd7AtrfySTmnH9lKu3DUAQ+UQEk3lE/zlbeUkPnnc0zACjO3Yd?= =?us-ascii?Q?JaTKdCalhHkECFTGRRNHc4PhEL0TCr5IVa9ql/JW7nxqGVRPuV/yF39Bcs6l?= =?us-ascii?Q?1NS5rjFyw8PZ87w4xOhbKCRBdKDtGvu+flcf0mBkZ1NaTqLfXyGpk0AOq1Bd?= =?us-ascii?Q?zmZHgIgKe419TX/2oaEaJ4kGdAaCHCoUq+sO9IxaSHSVawu4IPTMICazAo94?= =?us-ascii?Q?gq+73oNVPnFOj4ptH4XDaQ2/WgTS2PynvFV8VZJjqokyPotWBjwkFmQzb4o2?= =?us-ascii?Q?7k56X5++fuHq+ge5dOEcdIEsXB9fLN7UhgSDSdRBTklCOLR2UjEMio7YnGtg?= =?us-ascii?Q?7B6/3+8aQvlyOB/a6rHbz6S5rOTXAdmmc0xSqfLtZk+syVDZ8B/EDfPCKTD5?= =?us-ascii?Q?1OEf5943eU8podc+p59ZyPRyrhi8MH8GbPqS/xiHMiKamS7P7MnHFFhmxc4Z?= =?us-ascii?Q?FFSTjTaG0w+wDXfMOgu7771v7iH9bkMHYBJezxBmN4ry/QXK35einek27Wc9?= =?us-ascii?Q?Cu0dq6Ve3A=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 23c0af89-fca1-4174-c2e8-08df041c12ed X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Aug 2026 09:17:53.5294 (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: j6N9tE578rIwyPbi5XPQA6qQEPOvgwu0OZJkglqvHSHB/5pneQwL2nbm/BKCFfC2kZ9WIhTYGfULyl2h+vF5nQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB7687 On Thu, Aug 27, 2026 at 02:36:04AM +0900, Baul Lee wrote: > vxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every > MDBE_ATTR_SRC_LIST member, accepts the all-zeros address. > > A source list is only accepted on a (*, G) entry, whose source is the > all-zeros address, and for each member of the list an (S, G) entry is > derived from it by substituting the source. Entries are keyed by a plain > memcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present > and holds the all-zeros address and the source list holds it as well, the > derived (S, G) key is byte-identical to the (*, G) key and resolves to the > same entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is > then left with a zero address family. > > vxlan_mdb_remote_src_del() removes the forwarding entry of a source before > freeing the source entry: > > vxlan_mdb_remote_src_fwd_del(vxlan, group, remote, &ent->addr); > vxlan_mdb_remote_src_entry_del(ent); > > With the keys aliased, the first call deletes the remote of the entry that > owns 'ent' instead of a separate (S, G) entry, and frees 'ent'. The second > call then runs on the freed entry, and its hlist_del() reads ->pprev and > ->next out of it and writes through them. > > Adding the (*, G) entry with NLM_F_REPLACE and no source list marks the > all-zeros source for deletion and reaches this from the sweep at the end > of vxlan_mdb_remote_srcs_replace(). [...] > The MDB operations are netns-scoped, so an unprivileged user can perform > them in a new user and network namespace. > > Reject the all-zeros address in vxlan_mdb_is_valid_source(), which covers > both call sites. A (*, G) entry is expressed by omitting the source, so > nothing legitimate is refused. > > Discovered by XBOW, triaged by Baul Lee > > Fixes: a3a48de5eade ("vxlan: mdb: Add MDB control path support") > Signed-off-by: Baul Lee Reviewed-by: Ido Schimmel