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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?gnsYiUYa/hKztFs2H17tKZWKV81PvX2mMNkDeBfRKqPoyORFhC2v+F6BixUD?= =?us-ascii?Q?NYkJj1zWBLhq2lV7Yugh9MgWzT6L5XFDmeJFSzPBA9iu6ODA60dV8X9+tx5P?= =?us-ascii?Q?rMFUYwFVGZVFw80+VZzd80fQ2oVy5QqKdxI9vHU5pdA1ia8W8Br4muiYmkFH?= =?us-ascii?Q?/Rp53CZ+Z8M4tABC1PjhWwTBv2lWqXt49LWpxmtAAgNC9mrhwCa6hnWtHPBy?= =?us-ascii?Q?UYORj4OcmqCxIltWKjtgi9Wcm4NmtJlP6oHSJinTutBjK9wx/HYDyU6f1oLD?= =?us-ascii?Q?bY6eNiPlxZlCgbCLguGOO8nh1hSeSDulxTK8cna4HIaQD1vlkSeHhnCpuB3T?= =?us-ascii?Q?2ZOmSRq17I41nH+fK19pDBQB/Mr0fW8gAAqQ8j/R44RauUrym2ccMdyqdVcp?= =?us-ascii?Q?BOUZBdMK3xky+Li29d/ASaIIYG3L+w7ESOrckbLe//MTxLPgbe1/fPEZiCZ4?= =?us-ascii?Q?hGsOEyQBJwSrEp2cTzWI9V+mt+z+dS2QJagOmMA1sOb0gNhWF9PurF6pGIvS?= =?us-ascii?Q?BVe3DBiqo9Wf2Knn7ro9oF45FbPsffJZPVoKZSzEUf2FJc5e+dBMJ0oij0/G?= =?us-ascii?Q?w+psjnXdYcrvkWnleDswcvKGGsbMhLDMsZ34LGhlTNogkjGxi7YuqV0TpFEL?= =?us-ascii?Q?AjUdRgfTMNsnmsFbWiGo0WM9wnszw7ix9BqNi9V3egyhfxajhUk/p76j21L6?= =?us-ascii?Q?lC9ZBFeshcujjO8/HLbX5+0lGLQtfK9lc7WMaKCKg/dVRUBYIxAzcHShhu9c?= =?us-ascii?Q?9DgdBceCbYY+eC7/cuO1gL3QlzTkCvI0RjaiFL95ltQW7v44u9kSo0Fd8unO?= =?us-ascii?Q?AZYNR8XiVHj/2d3RiCzyL2jLV/c88xQ5VCFtUKTFBu0uSC0cz9TrlgWFxsSz?= =?us-ascii?Q?ldvQZ8pbTCAWBBCc1bRtTJwb+x2oyr0N6xW6gmHGReEA9tzQBiMPqUv3ernt?= =?us-ascii?Q?LkUSjdeJ9Bs3vgaz+GIvr//3S2yirxWd6lmEbUL2gJvtYnAZhRZXFi1suuC9?= =?us-ascii?Q?PLeHkrFTacCF9BeKrYiTWPXiMfQGz4zNDpEHz30R6I4ciMRcfy/jncLELlsK?= =?us-ascii?Q?c0hKhrFoN91QMvP5nfEF8t5E9HgpQQ3U25AvCisvfkkjnWFYbtUiCN4TuBIh?= =?us-ascii?Q?MXPR8bv20AD2dhEObN2pEFqcpybfB4fiiztSF9lHZMgc5D7PAcOizKO2BFpG?= =?us-ascii?Q?smcRoSCpDq0fEfJw7KqX+uxhmVJwkfnM1/AnXM84/Y6Zgf53IvgMAT1b2TM3?= =?us-ascii?Q?cVvz2x+/clH8aTCbS2O76XU66x+Krtg5+eeB6iypzvx9ERNIhQOGHKTPYpXq?= =?us-ascii?Q?QHx+0GW7SuuHVb9EbxGcKkiyplnViWUl8SY3RTOvTefgoZdN2lYnOVXy8i+i?= =?us-ascii?Q?VyxJWqDac1IhtzdU1wU3v0jRSWo4kXZaBdWNz+Z7SiG22b6XKxIDlo3vY31G?= =?us-ascii?Q?HhpjwAH2qzRQ2LOFvAT08OJL2ED2rd0Rywy3hIpVOoFDKhHSOGhn+FvVpI0b?= =?us-ascii?Q?yqjH6tR/y4U8iLsTBivm5EjbugP/dhkkZDXQCGgwkzLFtCUBUweJgPoMftP4?= =?us-ascii?Q?pe9fjuSARbVKWbNwdOCxzPW7v3Sq2pidXXyHKp1nyonTym4JvZkLJYgdl7rH?= =?us-ascii?Q?iBMPotwRCxVPZbx2l0inlAJObovgz5AzgK5J4cyPvrvn5dApZfQ378A3TL62?= =?us-ascii?Q?ZreBSvx+7lCkXGv5ZCmJjZP+8YM8mUsLmozjzfus6VM7yFTt?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d6d4e468-8d48-4164-8a5d-08df0c0d89c2 X-MS-Exchange-CrossTenant-AuthSource: PH0PR12MB7957.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Sep 2026 11:53:59.6576 (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: PfsoeT6ecKWrUwgAEZbKHJAESF0lnblh81+O/Zthzscio/x4LS3nHAyVqQa/qp960/M0q68ZJTcSmYl9++UaxA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8972 On Fri, Sep 04, 2026 at 06:06:44PM +0000, Naman Gulati wrote: > syzbot reported a null-ptr-deref in __ip6_del_rt_siblings() [0]. > > The stack trace hinted towards a null dereference of rt->fib6_node when > fn->leaf is accessed in __ip6_del_rt_siblings(). With > RTNL_FLAG_DOIT_UNLOCKED set, inet6_rtm_delroute() operations run > concurrently without acquiring the RTNL lock. In ip6_route_del(), the > route lookup happens under rcu_read_lock() without acquiring > table->tb6_lock. > > Between ip6_route_del() looking up the route and __ip6_del_rt_siblings() > acquiring table->tb6_lock, another thread can modify the routing table. > For example, when an ECMP route is replaced via RTM_NEWROUTE with > NLM_F_REPLACE, fib6_add_rt2node() unlinks all old siblings and sets > iter->fib6_node = NULL. A reproducer was found that triggers this [1]. > > Add a check to ensure rt->fib6_node is non-null before accessing it. [...] > Fixes: bd11ff421d36 ("ipv6: Get rid of RTNL for SIOCDELRT and RTM_DELROUTE.") > Reported-by: syzbot+a73e5ee0fd534fed75bd@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/netdev/6a9b03f9.04649fcc.10325f.0003.GAE@google.com > Signed-off-by: Naman Gulati > Reviewed-by: Kuniyuki Iwashima Reviewed-by: Ido Schimmel Sashiko-gemini flagged a pre-existing and unrelated issue that looks valid. I will check it.