=============================
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
5 locks held by udevd/4298:
#0: ffffffff8c1f0a88 (remove_cache_srcu){....}-{0:0}, at: rcu_lock_acquire+0x0/0x30
#1: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#2: ffff888074dbe148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#3: ffff888074dbe108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#3: ffff888074dbe108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#4: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 1 PID: 4298 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
cake_dequeue+0x1b8f/0x4aa0 net/sched/sch_cake.c:2189
qdisc_peek_dequeued+0x6e/0x1f0 include/net/sch_generic.h:1115
tbf_dequeue+0x7d/0xce0 net/sched/sch_tbf.c:265
dequeue_skb net/sched/sch_generic.c:292 [inline]
qdisc_restart net/sched/sch_generic.c:397 [inline]
__qdisc_run+0x237/0x1480 net/sched/sch_generic.c:415
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:132
net_tx_action+0x6bc/0x870 net/core/dev.c:5128
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:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
Code: 74 05 e8 2e 47 cc f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 f6 d4 9f f7 65 8b 05 97 d4 50 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900033ef920 EFLAGS: 00000206
RAX: df90c3dd0688b600 RBX: 0000000000000a06 RCX: df90c3dd0688b600
RDX: dffffc0000000000 RSI: ffffffff8a0b15c0 RDI: 0000000000000001
RBP: ffffc900033ef9a8 R08: dffffc0000000000 R09: ffffed1002d08139
R10: ffffed1002d08139 R11: 1ffff11002d08138 R12: dffffc0000000000
R13: ffffffff7fffffff R14: ffff8880168409c0 R15: 1ffff9200067df24
spin_unlock_irqrestore include/linux/spinlock.h:418 [inline]
__unfreeze_partials+0x161/0x200 mm/slub.c:2500
put_cpu_partial+0x12d/0x190 mm/slub.c:2587
qlist_free_all+0x35/0x90 mm/kasan/quarantine.c:176
kasan_quarantine_reduce+0x150/0x160 mm/kasan/quarantine.c:283
__kasan_slab_alloc+0x2f/0xd0 mm/kasan/common.c:444
kasan_slab_alloc include/linux/kasan.h:254 [inline]
slab_post_alloc_hook+0x4c/0x380 mm/slab.h:519
slab_alloc_node mm/slub.c:3220 [inline]
slab_alloc mm/slub.c:3228 [inline]
kmem_cache_alloc+0x100/0x290 mm/slub.c:3233
getname_flags+0xb5/0x500 fs/namei.c:138
user_path_at_empty+0x2a/0x190 fs/namei.c:2882
do_readlinkat+0xd4/0x480 fs/stat.c:442
__do_sys_readlink fs/stat.c:475 [inline]
__se_sys_readlink fs/stat.c:472 [inline]
__x64_sys_readlink+0x7b/0x90 fs/stat.c:472
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: 0033:0x7f42cab0e3a7
Code: 00 00 90 48 83 ec 10 48 63 ff 45 31 c9 45 31 c0 6a 00 31 c9 e8 8a 20 f9 ff 48 83 c4 18 c3 0f 1f 44 00 00 b8 59 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 8b 15 21 ba 0d 00 f7 d8 64 89 02 48
RSP: 002b:00007ffdda250868 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00007ffdda250d40 RCX: 00007f42cab0e3a7
RDX: 0000000000000400 RSI: 00007ffdda250870 RDI: 00007ffdda250d40
RBP: 00007ffdda250870 R08: 0000000000000000 R09: 0000000000000020
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000400
R13: 00007ffdda251575 R14: 0000561b8d0d7ca4 R15: 0000561b8d0d7bcc
----------------
Code disassembly (best guess):
0: 74 05 je 0x7
2: e8 2e 47 cc f7 call 0xf7cc4735
7: 48 c7 44 24 20 00 00 movq $0x0,0x20(%rsp)
e: 00 00
10: 9c pushf
11: 8f 44 24 20 pop 0x20(%rsp)
15: f6 44 24 21 02 testb $0x2,0x21(%rsp)
1a: 75 4b jne 0x67
1c: f7 c3 00 02 00 00 test $0x200,%ebx
22: 74 01 je 0x25
24: fb sti
25: bf 01 00 00 00 mov $0x1,%edi
* 2a: e8 f6 d4 9f f7 call 0xf79fd525 <-- trapping instruction
2f: 65 8b 05 97 d4 50 76 mov %gs:0x7650d497(%rip),%eax # 0x7650d4cd
36: 85 c0 test %eax,%eax
38: 74 3c je 0x76
3a: 48 rex.W
3b: c7 .byte 0xc7
3c: 04 24 add $0x24,%al
3e: 0e (bad)
3f: 36 ss