=============================
WARNING: suspicious RCU usage
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 syz.4.295/5514:
#0: ffff88802465a598 (&u->iolock){+.+.}-{3:3}, at: __unix_dgram_recvmsg+0x1e1/0xd50 net/unix/af_unix.c:2312
#1: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
#2: ffff88807a216148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#3: ffff88807a216108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
#3: ffff88807a216108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#4: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
stack backtrace:
CPU: 1 PID: 5514 Comm: syz.4.295 Not tainted 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:2199
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:constant_test_bit arch/x86/include/asm/bitops.h:207 [inline]
RIP: 0010:test_bit include/asm-generic/bitops/instrumented-non-atomic.h:135 [inline]
RIP: 0010:scm_has_secdata include/net/scm.h:111 [inline]
RIP: 0010:scm_recv+0x463/0x540 include/net/scm.h:128
Code: 28 00 00 00 48 3b 84 24 a0 00 00 00 75 56 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 4c 89 ff be 08 00 00 00 e8 2d 05 34 f9 <43> 80 3c 2e 00 74 08 4c 89 ff e8 8e 03 34 f9 4d 8b 37 4c 89 f6 48
RSP: 0018:ffffc90003a27660 EFLAGS: 00000256
RAX: 1ffff92000744f01 RBX: ffffc90003a27800 RCX: ffffffff88882f53
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff8880712f6008
RBP: ffffc90003a27750 R08: dffffc0000000000 R09: ffffed100e25ec02
R10: ffffed100e25ec02 R11: 1ffff1100e25ec01 R12: ffffc90003a27808
R13: dffffc0000000000 R14: 1ffff1100e25ec01 R15: ffff8880712f6008
__unix_dgram_recvmsg+0x9bf/0xd50 net/unix/af_unix.c:2392
____sys_recvmsg+0x291/0x580 net/socket.c:-1
___sys_recvmsg+0x1af/0x4f0 net/socket.c:2697
do_recvmmsg+0x344/0x7a0 net/socket.c:2791
__sys_recvmmsg net/socket.c:2870 [inline]
__do_sys_recvmmsg net/socket.c:2893 [inline]
__se_sys_recvmmsg net/socket.c:2886 [inline]
__x64_sys_recvmmsg+0x18d/0x240 net/socket.c:2886
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: 0033:0x7ff060873ba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff05eaba038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007ff060abb090 RCX: 00007ff060873ba9
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007ff0608f6e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff060abb128 R14: 00007ff060abb090 R15: 00007fffebe70d68
----------------
Code disassembly (best guess):
0: 28 00 sub %al,(%rax)
2: 00 00 add %al,(%rax)
4: 48 3b 84 24 a0 00 00 cmp 0xa0(%rsp),%rax
b: 00
c: 75 56 jne 0x64
e: 48 8d 65 d8 lea -0x28(%rbp),%rsp
12: 5b pop %rbx
13: 41 5c pop %r12
15: 41 5d pop %r13
17: 41 5e pop %r14
19: 41 5f pop %r15
1b: 5d pop %rbp
1c: c3 ret
1d: 4c 89 ff mov %r15,%rdi
20: be 08 00 00 00 mov $0x8,%esi
25: e8 2d 05 34 f9 call 0xf9340557
* 2a: 43 80 3c 2e 00 cmpb $0x0,(%r14,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 ff mov %r15,%rdi
34: e8 8e 03 34 f9 call 0xf93403c7
39: 4d 8b 37 mov (%r15),%r14
3c: 4c 89 f6 mov %r14,%rsi
3f: 48 rex.W