=============================
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
7 locks held by syz.0.515/6256:
#0: ffff88805d242460 (sb_writers#3){.+.+}-{0:0}, at: do_coredump+0x1492/0x2ac0 fs/coredump.c:893
#1: ffff888078448828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
#1: ffff888078448828 (&mm->mmap_lock){++++}-{3:3}, at: get_dump_page+0xe7/0x680 mm/gup.c:1836
#2: ffff888028874138 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#2: ffff888028874138 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: follow_page_pte+0x1e1/0xc20 mm/gup.c:528
#3: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#4: ffff88807e27d948 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6d9/0x880 net/core/dev.c:5154
#5: ffff88807e27d908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#5: ffff88807e27d908 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x311/0x4b0 net/sched/sch_generic.c:357
#6: ffffffff8c31eb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 6256 Comm: syz.0.515 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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:1125
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:5154
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:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:202
Code: 66 2e 0f 1f 84 00 00 00 00 00 53 48 89 fb e8 17 00 00 00 48 8b 3d d0 bd 10 0c 48 89 de 5b e9 27 55 44 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d 24 3b 89 7e 65 8b 15 25 3b 89 7e 81 e2 00
RSP: 0000:ffffc9000335f108 EFLAGS: 00000246
RAX: ffffffff81aced03 RBX: ffff88801ec7aea0 RCX: ffff88807ecf0000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200066be10 R12: 000ffffffffff000
R13: 0000000000000001 R14: 0000000000000000 R15: 8000000059e56025
follow_page_pte+0x54b/0xc20 mm/gup.c:550
follow_pmd_mask mm/gup.c:-1 [inline]
follow_pud_mask mm/gup.c:788 [inline]
follow_p4d_mask mm/gup.c:814 [inline]
follow_page_mask+0xa6e/0x12d0 mm/gup.c:873
__get_user_pages+0x3eb/0x11e0 mm/gup.c:1195
__get_user_pages_locked mm/gup.c:1382 [inline]
get_dump_page+0x190/0x680 mm/gup.c:1838
dump_user_range+0x54/0x340 fs/coredump.c:1013
elf_core_dump+0x2fbd/0x3500 fs/binfmt_elf.c:2285
do_coredump+0x14c7/0x2ac0 fs/coredump.c:894
get_signal+0x40a/0x12c0 kernel/signal.c:2886
arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:320
exc_page_fault+0x88/0x100 arch/x86/mm/fault.c:1499
asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0033:0x7efdc38bcde1
Code: 00 00 00 00 0f 1f 44 00 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 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
RSP: 002b:fffffffffffffe70 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007efdc3b36090 RCX: 00007efdc38bcdd9
RDX: 0000000000000000 RSI: fffffffffffffe70 RDI: 0000000000008000
RBP: 00007efdc3952d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007efdc3b36128 R14: 00007efdc3b36090 R15: 00007ffdbb86ace8
----------------
Code disassembly (best guess):
0: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
7: 00 00 00
a: 53 push %rbx
b: 48 89 fb mov %rdi,%rbx
e: e8 17 00 00 00 call 0x2a
13: 48 8b 3d d0 bd 10 0c mov 0xc10bdd0(%rip),%rdi # 0xc10bdea
1a: 48 89 de mov %rbx,%rsi
1d: 5b pop %rbx
1e: e9 27 55 44 00 jmp 0x44554a
23: 00 00 add %al,(%rax)
25: cc int3
26: cc int3
27: 00 00 add %al,(%rax)
29: cc int3
* 2a: 48 8b 04 24 mov (%rsp),%rax <-- trapping instruction
2e: 65 48 8b 0d 24 3b 89 mov %gs:0x7e893b24(%rip),%rcx # 0x7e893b5a
35: 7e
36: 65 8b 15 25 3b 89 7e mov %gs:0x7e893b25(%rip),%edx # 0x7e893b62
3d: 81 .byte 0x81
3e: e2 00 loop 0x40