[syzbot] [net?] WARNING: refcount bug in nsim_fib_event_nb (3)
From: syzbot <hidden>
Date: 2026-06-10 06:11:30
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Hello, syzbot found the following issue on: HEAD commit: 6f3ed7fec72f Merge tag 'for-7.1/dm-fixes-3' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=1144db7e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=bd38685893011045 dashboard link: https://syzkaller.appspot.com/bug?extid=cb2aa2390ac024e25f5c compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/625fc484e456/disk-6f3ed7fe.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/fd23de5678d1/vmlinux-6f3ed7fe.xz kernel image: https://storage.googleapis.com/syzbot-assets/5395fddce64e/bzImage-6f3ed7fe.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+cb2aa2390ac024e25f5c@syzkaller.appspotmail.com ------------[ 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/u8:8/1044 Modules linked in: CPU: 1 UID: 0 PID: 1044 Comm: kworker/u8:8 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 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 4b 36 23 fd 48 8d 3d 14 85 f1 0a 67 48 0f b9 3a eb 4a e8 38 36 23 fd 48 8d 3d 11 85 f1 0a <67> 48 0f b9 3a eb 37 e8 25 36 23 fd 48 8d 3d 0e 85 f1 0a 67 48 0f RSP: 0018:ffffc90005e4f270 EFLAGS: 00010293 RAX: ffffffff84a135d8 RBX: 0000000000000002 RCX: ffff888027863d80 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8f92baf0 RBP: 0000000000000000 R08: ffff888027863d80 R09: 0000000000000005 R10: 0000000000000100 R11: 0000000000000004 R12: ffff8880117bd000 R13: dffffc0000000000 R14: ffff88803392903c R15: ffff8880117bd000 FS: 0000000000000000(0000) GS:ffff888126283000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000557b57a3d220 CR3: 00000000352b4000 CR4: 00000000003526f0 Call Trace: <TASK> __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:25 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:70 [inline] register_fib_notifier+0x184/0x360 net/core/fib_notifier.c:108 nsim_fib_create+0x85d/0x9f0 drivers/net/netdevsim/fib.c:1596 nsim_dev_reload_create drivers/net/netdevsim/dev.c:1604 [inline] nsim_dev_reload_up+0x374/0x7c0 drivers/net/netdevsim/dev.c:1058 devlink_reload+0x501/0x8d0 net/devlink/dev.c:475 devlink_pernet_pre_exit+0x1ff/0x420 net/devlink/core.c:558 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:702 process_one_work kernel/workqueue.c:3314 [inline] process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3397 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3478 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> ---------------- 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 4b 36 23 fd call 0xfd23365b 10: 48 8d 3d 14 85 f1 0a lea 0xaf18514(%rip),%rdi # 0xaf1852b 17: 67 48 0f b9 3a ud1 (%edx),%rdi 1c: eb 4a jmp 0x68 1e: e8 38 36 23 fd call 0xfd23365b 23: 48 8d 3d 11 85 f1 0a lea 0xaf18511(%rip),%rdi # 0xaf1853b * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: eb 37 jmp 0x68 31: e8 25 36 23 fd call 0xfd23365b 36: 48 8d 3d 0e 85 f1 0a lea 0xaf1850e(%rip),%rdi # 0xaf1854b 3d: 67 addr32 3e: 48 rex.W 3f: 0f .byte 0xf --- This report is generated by a bot. 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