syzbot

======================================================
WARNING: possible circular locking dependency detected
5.15.189-syzkaller #0 Not tainted
------------------------------------------------------
udevd/3562 is trying to acquire lock:
ffff8880796e9db8 (&trie->lock){....}-{2:2}, at: trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467

but task is already holding lock:
ffff8880b912a218 (hrtimer_bases.lock){-.-.}-{2:2}, at: lock_hrtimer_base kernel/time/hrtimer.c:168 [inline]
ffff8880b912a218 (hrtimer_bases.lock){-.-.}-{2:2}, at: hrtimer_start_range_ns+0xff/0xc20 kernel/time/hrtimer.c:1289

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (hrtimer_bases.lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
       lock_hrtimer_base kernel/time/hrtimer.c:168 [inline]
       hrtimer_start_range_ns+0xff/0xc20 kernel/time/hrtimer.c:1289
       hrtimer_start include/linux/hrtimer.h:420 [inline]
       run_page_cache_worker kernel/rcu/tree.c:3492 [inline]
       kvfree_call_rcu+0x60d/0x7c0 kernel/rcu/tree.c:3603
       rtnl_register_internal+0x44e/0x540 net/core/rtnetlink.c:223
       rtnl_register+0x2e/0x70 net/core/rtnetlink.c:273
       ip_rt_init+0x2e0/0x3a0 net/ipv4/route.c:3795
       ip_init+0xa/0x20 net/ipv4/ip_output.c:1749
       inet_init+0x28b/0x3a0 net/ipv4/af_inet.c:2007
       do_one_initcall+0x1ee/0x680 init/main.c:1302
       do_initcall_level+0x137/0x1f0 init/main.c:1375
       do_initcalls+0x4b/0x90 init/main.c:1391
       kernel_init_freeable+0x3ce/0x560 init/main.c:1615
       kernel_init+0x19/0x1b0 init/main.c:1506
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

-> #1 (krc.lock){..-.}-{2:2}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
       krc_this_cpu_lock kernel/rcu/tree.c:3203 [inline]
       add_ptr_to_bulk_krc_lock kernel/rcu/tree.c:3510 [inline]
       kvfree_call_rcu+0x186/0x7c0 kernel/rcu/tree.c:3601
       trie_delete_elem+0x58c/0x710 kernel/bpf/lpm_trie.c:-1
       0xffffffffa001a8ce
       bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
       __bpf_prog_run include/linux/filter.h:628 [inline]
       bpf_prog_run include/linux/filter.h:635 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
       bpf_trace_run2+0x15b/0x2d0 kernel/trace/bpf_trace.c:1915
       __bpf_trace_sys_enter+0x60/0x70 include/trace/events/syscalls.h:18
       trace_sys_enter+0x65/0x80 include/trace/events/syscalls.h:18
       syscall_trace_enter+0x115/0x180 kernel/entry/common.c:77
       do_syscall_64+0x24/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&trie->lock){....}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
       trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467
       bpf_prog_2c29ac5cdc6b1842+0x3a/0x4cc
       bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
       __bpf_prog_run include/linux/filter.h:628 [inline]
       bpf_prog_run include/linux/filter.h:635 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
       bpf_trace_run2+0x15b/0x2d0 kernel/trace/bpf_trace.c:1915
       trace_hrtimer_start include/trace/events/timer.h:199 [inline]
       debug_activate kernel/time/hrtimer.c:466 [inline]
       enqueue_hrtimer+0x314/0x370 kernel/time/hrtimer.c:1074
       __hrtimer_start_range_ns kernel/time/hrtimer.c:1249 [inline]
       hrtimer_start_range_ns+0xa7e/0xc20 kernel/time/hrtimer.c:1291
       hrtimer_start_expires include/linux/hrtimer.h:434 [inline]
       hrtimer_sleeper_start_expires kernel/time/hrtimer.c:1970 [inline]
       schedule_hrtimeout_range_clock+0x3a4/0x560 kernel/time/hrtimer.c:2318
       ep_poll+0x1739/0x19a0 fs/eventpoll.c:1918
       do_epoll_wait+0x1a1/0x210 fs/eventpoll.c:2296
       __do_sys_epoll_wait fs/eventpoll.c:2308 [inline]
       __se_sys_epoll_wait fs/eventpoll.c:2303 [inline]
       __x64_sys_epoll_wait+0x1bb/0x200 fs/eventpoll.c:2303
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &trie->lock --> krc.lock --> hrtimer_bases.lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(hrtimer_bases.lock);
                               lock(krc.lock);
                               lock(hrtimer_bases.lock);
  lock(&trie->lock);

 *** DEADLOCK ***

2 locks held by udevd/3562:
 #0: ffff8880b912a218 (hrtimer_bases.lock){-.-.}-{2:2}, at: lock_hrtimer_base kernel/time/hrtimer.c:168 [inline]
 #0: ffff8880b912a218 (hrtimer_bases.lock){-.-.}-{2:2}, at: hrtimer_start_range_ns+0xff/0xc20 kernel/time/hrtimer.c:1289
 #1: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:
CPU: 1 PID: 3562 Comm: udevd Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
 trie_delete_elem+0x90/0x710 kernel/bpf/lpm_trie.c:467
 bpf_prog_2c29ac5cdc6b1842+0x3a/0x4cc
 bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline]
 __bpf_prog_run include/linux/filter.h:628 [inline]
 bpf_prog_run include/linux/filter.h:635 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline]
 bpf_trace_run2+0x15b/0x2d0 kernel/trace/bpf_trace.c:1915
 trace_hrtimer_start include/trace/events/timer.h:199 [inline]
 debug_activate kernel/time/hrtimer.c:466 [inline]
 enqueue_hrtimer+0x314/0x370 kernel/time/hrtimer.c:1074
 __hrtimer_start_range_ns kernel/time/hrtimer.c:1249 [inline]
 hrtimer_start_range_ns+0xa7e/0xc20 kernel/time/hrtimer.c:1291
 hrtimer_start_expires include/linux/hrtimer.h:434 [inline]
 hrtimer_sleeper_start_expires kernel/time/hrtimer.c:1970 [inline]
 schedule_hrtimeout_range_clock+0x3a4/0x560 kernel/time/hrtimer.c:2318
 ep_poll+0x1739/0x19a0 fs/eventpoll.c:1918
 do_epoll_wait+0x1a1/0x210 fs/eventpoll.c:2296
 __do_sys_epoll_wait fs/eventpoll.c:2308 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2303 [inline]
 __x64_sys_epoll_wait+0x1bb/0x200 fs/eventpoll.c:2303
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fb23845e407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fffa6a4e030 EFLAGS: 00000202 ORIG_RAX: 00000000000000e8
RAX: ffffffffffffffda RBX: 00007fb238370880 RCX: 00007fb23845e407
RDX: 0000000000000008 RSI: 00007fffa6a4e190 RDI: 000000000000000b
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000bb8 R11: 0000000000000202 R12: 0000000000000000
R13: 000055a325c09100 R14: 0000000000000000 R15: 00007fffa6a4e280
 </TASK>