=============================
WARNING: suspicious RCU usage
5.15.189-syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 1
6 locks held by udevd/4399:
#0: ffff88807653c028 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88807653c028 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x15d/0x2b0 mm/util.c:549
#1: ffffc90000007be0 ((&d->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#1: ffffc90000007be0 ((&d->timer)){+.-.}-{0:0}, at: call_timer_fn+0xbb/0x530 kernel/time/timer.c:1441
#2: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
#3: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#4: ffff88805fa26108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#4: ffff88805fa26108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline]
#4: ffff88805fa26108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253
#5: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 0 PID: 4399 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:
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:793
pfifo_tail_enqueue+0x372/0x4d0 net/sched/sch_fifo.c:54
qdisc_enqueue include/net/sch_generic.h:832 [inline]
tbf_enqueue+0x224/0x6e0 net/sched/sch_tbf.c:243
dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3852
__dev_xmit_skb net/core/dev.c:3936 [inline]
__dev_queue_xmit+0xd7e/0x2ed0 net/core/dev.c:4253
tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
tipc_bearer_xmit_skb+0x292/0x3c0 net/tipc/bearer.c:577
tipc_disc_timeout+0x568/0x6b0 net/tipc/discover.c:338
call_timer_fn+0x16c/0x530 kernel/time/timer.c:1451
expire_timers kernel/time/timer.c:1496 [inline]
__run_timers+0x525/0x7c0 kernel/time/timer.c:1767
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
handle_softirqs+0x328/0x820 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:rb_next+0x94/0xd0 lib/rbtree.c:517
Code: 58 10 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 e3 48 89 df e8 4e 62 bf fd eb d9 49 3b 5e 08 4c 89 f3 75 a3 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 2d 62 bf fd 4c 8b 33 49 83 e6 fc
RSP: 0018:ffffc900043cfaf0 EFLAGS: 00000a02
RAX: 1ffff1100e604e25 RBX: ffff888073027128 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff888073027130
RBP: 1ffff1100e604ea5 R08: dffffc0000000000 R09: ffffed100eca77f0
R10: ffffed100eca77f0 R11: 1ffff1100eca77ef R12: ffff888073027548
R13: dffffc0000000000 R14: ffff888073027128 R15: dffffc0000000000
browse_rb mm/mmap.c:337 [inline]
validate_mm+0x513/0x950 mm/mmap.c:422
mmap_region+0x10cf/0x15e0 mm/mmap.c:2935
do_mmap+0x77a/0xdf0 mm/mmap.c:1582
vm_mmap_pgoff+0x1b2/0x2b0 mm/util.c:551
ksys_mmap_pgoff+0x140/0x780 mm/mmap.c:1631
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: 0033:0x7f13bcaed822
Code: 00 00 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 76 5b 5d c3 0f 1f 00 48 8b 05 a1 35 0d 00 64
RSP: 002b:00007ffcfa744728 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f13bcaed822
RDX: 0000000000000003 RSI: 0000000000000200 RDI: 0000000000000000
RBP: 0000000000000022 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000563c26157850 R15: 00007f13bd1c73d8
----------------
Code disassembly (best guess):
0: 58 pop %rax
1: 10 48 89 adc %cl,-0x77(%rax)
4: d8 48 c1 fmuls -0x3f(%rax)
7: e8 03 42 80 3c call 0x3c80420f
c: 38 00 cmp %al,(%rax)
e: 74 e3 je 0xfffffff3
10: 48 89 df mov %rbx,%rdi
13: e8 4e 62 bf fd call 0xfdbf6266
18: eb d9 jmp 0xfffffff3
1a: 49 3b 5e 08 cmp 0x8(%r14),%rbx
1e: 4c 89 f3 mov %r14,%rbx
21: 75 a3 jne 0xffffffc6
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 38 00 cmpb $0x0,(%rax,%r15,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 2d 62 bf fd call 0xfdbf6266
39: 4c 8b 33 mov (%rbx),%r14
3c: 49 83 e6 fc and $0xfffffffffffffffc,%r14