=============================
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
6 locks held by udevd/4174:
#0: ffff88807b664728 (&mm->mmap_lock){++++}-{3:3}, at: __do_munmap+0x9c5/0xdf0 mm/mmap.c:2897
#1: ffff88807b664690 (&mm->page_table_lock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#1: ffff88807b664690 (&mm->page_table_lock){+.+.}-{2:2}, at: browse_rb mm/mmap.c:356 [inline]
#1: ffff88807b664690 (&mm->page_table_lock){+.+.}-{2:2}, at: validate_mm+0x31a/0x950 mm/mmap.c:423
#2: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#3: ffff888066762148 (dev->qdisc_running_key ?: &qdisc_running_key){+..-}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5141
#4: ffff888066762108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#4: ffff888066762108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
#5: ffffffff8c31eaa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 4174 Comm: udevd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
dump_stack_lvl+0x188/0x250 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:783
cake_dequeue+0x1bd6/0x4b10 net/sched/sch_cake.c:2205
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:295 [inline]
qdisc_restart net/sched/sch_generic.c:400 [inline]
__qdisc_run+0x236/0x1490 net/sched/sch_generic.c:418
qdisc_run+0x103/0x2f0 include/net/pkt_sched.h:131
net_tx_action+0x6d9/0x880 net/core/dev.c:5141
handle_softirqs+0x339/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 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:get_current arch/x86/include/asm/current.h:-1 [inline]
RIP: 0010:debug_spin_lock_before kernel/locking/spinlock_debug.c:86 [inline]
RIP: 0010:do_raw_spin_lock+0xc2/0x2f0 kernel/locking/spinlock_debug.c:114
Code: 24 10 80 3c 10 00 74 12 4c 89 f7 e8 d8 d4 5f 00 48 ba 00 00 00 00 00 fc ff df 4c 89 74 24 18 49 8b 06 65 48 8b 0d ee 17 a4 7e <48> 89 4c 24 08 48 39 c8 0f 84 1d 01 00 00 4c 8d 6b 08 4d 89 ef 49
RSP: 0018:ffffc900030cfc40 EFLAGS: 00000246
RAX: ffffffffffffffff RBX: ffff88807b664678 RCX: ffff88807a640000
RDX: dffffc0000000000 RSI: ffffffff8a2b3a20 RDI: ffff88807b664678
RBP: ffffc900030cfd00 R08: dffffc0000000000 R09: 1ffffffff203a418
R10: dffffc0000000000 R11: fffffbfff203a419 R12: 1ffff92000619f8c
R13: dffffc0000000000 R14: ffff88807b664688 R15: ffff88802a9bb420
spin_lock include/linux/spinlock.h:364 [inline]
browse_rb mm/mmap.c:356 [inline]
validate_mm+0x31a/0x950 mm/mmap.c:423
remove_vma_list mm/mmap.c:2631 [inline]
__do_munmap+0xcf3/0xdf0 mm/mmap.c:2902
__vm_munmap+0x140/0x240 mm/mmap.c:2952
__do_sys_munmap mm/mmap.c:2978 [inline]
__se_sys_munmap mm/mmap.c:2974 [inline]
__x64_sys_munmap+0x67/0x70 mm/mmap.c:2974
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: 0033:0x7fed13593097
Code: 73 01 c3 48 8b 0d 61 2d 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 31 2d 0d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffdbbedf118 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 0000559d7f2b0ef0 RCX: 00007fed13593097
RDX: 0000559d7f2b6aa8 RSI: 0000000000000200 RDI: 00007fed12adb000
RBP: 0000000000000008 R08: 0000000000000030 R09: 0000559d7f2af500
R10: 0000000000000040 R11: 0000000000000246 R12: 0000559d7f2aacb0
R13: 00007fed13c7239c R14: 0000000000001000 R15: 0000000000000009
----------------
Code disassembly (best guess):
0: 24 10 and $0x10,%al
2: 80 3c 10 00 cmpb $0x0,(%rax,%rdx,1)
6: 74 12 je 0x1a
8: 4c 89 f7 mov %r14,%rdi
b: e8 d8 d4 5f 00 call 0x5fd4e8
10: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx
17: fc ff df
1a: 4c 89 74 24 18 mov %r14,0x18(%rsp)
1f: 49 8b 06 mov (%r14),%rax
22: 65 48 8b 0d ee 17 a4 mov %gs:0x7ea417ee(%rip),%rcx # 0x7ea41818
29: 7e
* 2a: 48 89 4c 24 08 mov %rcx,0x8(%rsp) <-- trapping instruction
2f: 48 39 c8 cmp %rcx,%rax
32: 0f 84 1d 01 00 00 je 0x155
38: 4c 8d 6b 08 lea 0x8(%rbx),%r13
3c: 4d 89 ef mov %r13,%r15
3f: 49 rex.WB