------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#1: kworker/u8:6/157 Modules linked in: CPU: 1 UID: 0 PID: 157 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: netns cleanup_net RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25 Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 fb 2e 26 fd 48 8d 3d e4 46 d6 0a 67 48 0f b9 3a eb 4a e8 e8 2e 26 fd 48 8d 3d e1 46 d6 0a <67> 48 0f b9 3a eb 37 e8 d5 2e 26 fd 48 8d 3d de 46 d6 0a 67 48 0f RSP: 0018:ffffc90003ae7270 EFLAGS: 00010293 RAX: ffffffff849e4968 RBX: 0000000000000002 RCX: ffff88801ffb3d00 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8f749050 RBP: 0000000000000000 R08: ffff88801ffb3d00 R09: 0000000000000005 R10: 0000000000000100 R11: 0000000000000004 R12: ffff88807b5a9000 R13: dffffc0000000000 R14: ffff888035d31c3c R15: ffff88807b5a9000 FS: 0000000000000000(0000) GS:ffff888126439000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fbc3ca5d400 CR3: 000000005dbf2000 CR4: 00000000003526f0 Call Trace: __refcount_add include/linux/refcount.h:-1 [inline] __refcount_inc include/linux/refcount.h:366 [inline] refcount_inc include/linux/refcount.h:383 [inline] fib_info_hold include/net/ip_fib.h:629 [inline] nsim_fib4_prepare_event drivers/net/netdevsim/fib.c:930 [inline] nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:1000 [inline] nsim_fib_event_nb+0x1055/0x1240 drivers/net/netdevsim/fib.c:1043 call_fib_notifier+0x45/0x80 net/core/fib_notifier.c:24 call_fib_entry_notifier net/ipv4/fib_trie.c:90 [inline] fib_leaf_notify net/ipv4/fib_trie.c:2176 [inline] fib_table_notify net/ipv4/fib_trie.c:2194 [inline] fib_notify+0x36b/0x5e0 net/ipv4/fib_trie.c:2217 fib_net_dump net/core/fib_notifier.c:69 [inline] register_fib_notifier+0x184/0x360 net/core/fib_notifier.c:107 nsim_fib_create+0x85d/0x9f0 drivers/net/netdevsim/fib.c:1596 nsim_dev_reload_create drivers/net/netdevsim/dev.c:1583 [inline] nsim_dev_reload_up+0x374/0x7c0 drivers/net/netdevsim/dev.c:1058 devlink_reload+0x50e/0x8e0 net/devlink/dev.c:474 devlink_pernet_pre_exit+0x1ea/0x3f0 net/devlink/core.c:507 ops_pre_exit_list net/core/net_namespace.c:161 [inline] ops_undo_list+0x187/0x940 net/core/net_namespace.c:234 cleanup_net+0x56e/0x800 net/core/net_namespace.c:704 process_one_work kernel/workqueue.c:3276 [inline] process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 ---------------- Code disassembly (best guess): 0: eb 66 jmp 0x68 2: 85 db test %ebx,%ebx 4: 74 3e je 0x44 6: 83 fb 01 cmp $0x1,%ebx 9: 75 4c jne 0x57 b: e8 fb 2e 26 fd call 0xfd262f0b 10: 48 8d 3d e4 46 d6 0a lea 0xad646e4(%rip),%rdi # 0xad646fb 17: 67 48 0f b9 3a ud1 (%edx),%rdi 1c: eb 4a jmp 0x68 1e: e8 e8 2e 26 fd call 0xfd262f0b 23: 48 8d 3d e1 46 d6 0a lea 0xad646e1(%rip),%rdi # 0xad6470b * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: eb 37 jmp 0x68 31: e8 d5 2e 26 fd call 0xfd262f0b 36: 48 8d 3d de 46 d6 0a lea 0xad646de(%rip),%rdi # 0xad6471b 3d: 67 addr32 3e: 48 rex.W 3f: 0f .byte 0xf