=============================
WARNING: suspicious RCU usage
5.15.185-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 syz.3.123/4724:
#0: ffff88805b6a80e0 (&type->s_umount_key#28/1){+.+.}-{3:3}, at: alloc_super+0x201/0x950 fs/super.c:229
#1: ffffffff8c110ac0 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0xa7/0x150 kernel/printk/printk.c:2273
#2: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#3: ffff88807b35d148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#4: ffff88807b35d108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#4: ffff88807b35d108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#5: ffffffff8c11bfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 1 PID: 4724 Comm: syz.3.123 Not tainted 5.15.185-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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+0x213/0x4e0 net/sched/sch_api.c:800
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:console_unlock+0xd90/0x1200 kernel/printk/printk.c:2749
Code: 00 48 83 7c 24 28 00 75 19 e8 ec 9e 18 00 eb 18 e8 e5 9e 18 00 e8 80 49 42 08 48 83 7c 24 28 00 74 e7 e8 d3 9e 18 00 fb 31 ff <89> de e8 29 a2 18 00 85 db 0f 94 c0 22 44 24 17 3c 01 75 1f e8 b7
RSP: 0018:ffffc90003b6f5e0 EFLAGS: 00000246
RAX: ffffffff815f234d RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000c9f1000 RSI: 0000000000010d8c RDI: 0000000000000000
RBP: ffffc90003b6f850 R08: dffffc0000000000 R09: fffffbfff1ff3619
R10: fffffbfff1ff3619 R11: 1ffffffff1ff3618 R12: 1ffffffff194c725
R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffffffff194c71e
vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
_printk+0xcc/0x110 kernel/printk/printk.c:2299
__ext4_msg+0x1e8/0x200 fs/ext4/super.c:917
ext4_fill_super+0x9690/0x9a00 fs/ext4/super.c:5010
mount_bdev+0x287/0x3c0 fs/super.c:1400
legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x24a/0xa40 fs/namespace.c:3010
do_mount fs/namespace.c:3353 [inline]
__do_sys_mount fs/namespace.c:3561 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3538
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: 0033:0x7f504c8360ca
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f504a69be68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f504a69bef0 RCX: 00007f504c8360ca
RDX: 0000200000000100 RSI: 0000200000000280 RDI: 00007f504a69beb0
RBP: 0000200000000100 R08: 00007f504a69bef0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000000280
R13: 00007f504a69beb0 R14: 0000000000000ba6 R15: 0000200000000580
----------------
Code disassembly (best guess):
0: 00 48 83 add %cl,-0x7d(%rax)
3: 7c 24 jl 0x29
5: 28 00 sub %al,(%rax)
7: 75 19 jne 0x22
9: e8 ec 9e 18 00 call 0x189efa
e: eb 18 jmp 0x28
10: e8 e5 9e 18 00 call 0x189efa
15: e8 80 49 42 08 call 0x842499a
1a: 48 83 7c 24 28 00 cmpq $0x0,0x28(%rsp)
20: 74 e7 je 0x9
22: e8 d3 9e 18 00 call 0x189efa
27: fb sti
28: 31 ff xor %edi,%edi
* 2a: 89 de mov %ebx,%esi <-- trapping instruction
2c: e8 29 a2 18 00 call 0x18a25a
31: 85 db test %ebx,%ebx
33: 0f 94 c0 sete %al
36: 22 44 24 17 and 0x17(%rsp),%al
3a: 3c 01 cmp $0x1,%al
3c: 75 1f jne 0x5d
3e: e8 .byte 0xe8
3f: b7 .byte 0xb7