[syzbot ci] Re: [PATCH net] tipc: fix UAF race in tipc_mon_peer_up/down/remove_peer vs bearer teardown

[syzbot ci <syzbot+ci2d44e407aec2bd60@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v1] [PATCH net] tipc: fix UAF race in tipc_mon_peer_up/down/remove_peer vs bearer teardown
https://lore.kernel.org/all/20260415061211.45530-1-95986478+SnailSploit@users.noreply.github.com
* [PATCH] [PATCH net] tipc: fix UAF race in tipc_mon_peer_up/down/remove_peer vs bearer teardown

and found the following issue:
WARNING: suspicious RCU usage in tipc_mon_delete

Full report is available here:
https://ci.syzbot.org/series/6267bc07-4172-4821-b3e5-dac381479d9d

***

WARNING: suspicious RCU usage in tipc_mon_delete

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      35c2c39832e569449b9192fa1afbbc4c66227af7
arch:      amd64
compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config:    https://ci.syzbot.org/builds/a29dabe7-96d8-4072-bc2c-d798a349301e/config
syz repro: https://ci.syzbot.org/findings/f144d75a-7c29-41a1-988e-09892a89baa1/syz_repro

tipc: Disabling bearer <eth:syzkaller0>
=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/tipc/monitor.c:108 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.2.19/5962:
 #0: ffffffff8fbcba48 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff8fbcba48 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 drivers/net/tun.c:3438

stack backtrace:
CPU: 1 UID: 0 PID: 5962 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 lockdep_rcu_suspicious+0x13f/0x1d0 kernel/locking/lockdep.c:6876
 tipc_monitor_rcu_bh+0xf5/0x110 net/tipc/monitor.c:108
 get_self net/tipc/monitor.c:209 [inline]
 tipc_mon_delete+0x10b/0x4d0 net/tipc/monitor.c:704
 tipc_l2_device_event+0x370/0x680 net/tipc/bearer.c:-1
 notifier_call_chain+0x1be/0x400 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 unregister_netdevice_many_notify+0x17a5/0x22c0 net/core/dev.c:12464
 unregister_netdevice_many net/core/dev.c:12527 [inline]
 unregister_netdevice_queue+0x31f/0x360 net/core/dev.c:12337
 unregister_netdevice include/linux/netdevice.h:3427 [inline]
 __tun_detach+0x6d9/0x15d0 drivers/net/tun.c:621
 tun_detach drivers/net/tun.c:637 [inline]
 tun_chr_close+0x10a/0x1c0 drivers/net/tun.c:3438
 __fput+0x44f/0xa70 fs/file_table.c:469
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7b26d9c819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffec30cee78 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffec30cef60 RCX: 00007f7b26d9c819
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000011900 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2e520000 R11: 0000000000000246 R12: 00007ffec30cefa0
R13: 00007f7b27015fac R14: 000000000001193b R15: 00007f7b27015fa0
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.

To test a patch for this bug, please reply with `#syz test`
(should be on a separate line).

The patch should be attached to the email.
Note: arguments like custom git repos and branches are not supported.