=============================
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
8 locks held by syz.2.159/4883:
#0: ffff888078c38828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:117 [inline]
#0: ffff888078c38828 (&mm->mmap_lock){++++}-{3:3}, at: __mm_populate+0x15e/0x3a0 mm/gup.c:1618
#1: ffff888073689138 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#1: ffff888073689138 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: follow_page_pte+0x1e1/0xc20 mm/gup.c:528
#2: ffffc90000dd0be0 ((&d->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
#2: ffffc90000dd0be0 ((&d->timer)){+.-.}-{0:0}, at: call_timer_fn+0xbb/0x530 kernel/time/timer.c:1441
#3: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
#4: ffffffff8c11c7c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#5: ffff8880220e9108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#5: ffff8880220e9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline]
#5: ffff8880220e9108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253
#6: ffff8880220e9148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
#7: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 1 PID: 4883 Comm: syz.2.159 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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
netem_dequeue+0x12ba/0x1400 net/sched/sch_netem.c:766
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
__dev_xmit_skb net/core/dev.c:3942 [inline]
__dev_queue_xmit+0xeb9/0x2ed0 net/core/dev.c:4253
tipc_l2_send_msg+0x30a/0x3c0 net/tipc/bearer.c:518
tipc_bearer_xmit_skb+0x292/0x3c0 net/tipc/bearer.c:577
tipc_disc_timeout+0x568/0x6b0 net/tipc/discover.c:338
call_timer_fn+0x16c/0x530 kernel/time/timer.c:1451
expire_timers kernel/time/timer.c:1496 [inline]
__run_timers+0x525/0x7c0 kernel/time/timer.c:1767
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780
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:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x60 kernel/kcov.c:205
Code: 84 00 00 00 00 00 53 48 89 fb e8 17 00 00 00 48 8b 3d 50 d3 f1 0b 48 89 de 5b e9 57 9e 43 00 00 00 cc cc 00 00 cc 48 8b 04 24 <65> 48 8b 0d a4 a3 8a 7e 65 8b 15 a5 a3 8a 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc900033ef930 EFLAGS: 00000297
RAX: ffffffff81aa502d RBX: ffffea00016fcc00 RCX: ffff888021581dc0
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 0000000000040004
RBP: 0000000000001052 R08: 0000000000000004 R09: 0000000000000003
R10: fffff5200067df1c R11: 1ffff9200067df1c R12: 000ffffffffff000
R13: 1ffff11002efa0af R14: 0000000000000000 R15: 000000005bf30027
try_grab_page+0x3d/0x460 mm/gup.c:211
follow_page_pte+0x784/0xc20 mm/gup.c:584
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+0xdb5/0x11c0 mm/gup.c:1195
populate_vma_page_range+0x213/0x290 mm/gup.c:1529
__mm_populate+0x26f/0x3a0 mm/gup.c:1638
mm_populate include/linux/mm.h:2646 [inline]
vm_mmap_pgoff+0x203/0x2b0 mm/util.c:556
ksys_mmap_pgoff+0x140/0x780 mm/mmap.c:1635
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: 0033:0x7f5a853c36c9
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:00007f5a8362a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f5a85619fa0 RCX: 00007f5a853c36c9
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f5a85445f91 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a8561a038 R14: 00007f5a85619fa0 R15: 00007ffc95bbb848
----------------
Code disassembly (best guess):
0: 84 00 test %al,(%rax)
2: 00 00 add %al,(%rax)
4: 00 00 add %al,(%rax)
6: 53 push %rbx
7: 48 89 fb mov %rdi,%rbx
a: e8 17 00 00 00 call 0x26
f: 48 8b 3d 50 d3 f1 0b mov 0xbf1d350(%rip),%rdi # 0xbf1d366
16: 48 89 de mov %rbx,%rsi
19: 5b pop %rbx
1a: e9 57 9e 43 00 jmp 0x439e76
1f: 00 00 add %al,(%rax)
21: cc int3
22: cc int3
23: 00 00 add %al,(%rax)
25: cc int3
26: 48 8b 04 24 mov (%rsp),%rax
* 2a: 65 48 8b 0d a4 a3 8a mov %gs:0x7e8aa3a4(%rip),%rcx # 0x7e8aa3d6 <-- trapping instruction
31: 7e
32: 65 8b 15 a5 a3 8a 7e mov %gs:0x7e8aa3a5(%rip),%edx # 0x7e8aa3de
39: 81 e2 00 01 ff 00 and $0xff0100,%edx
3f: 74 .byte 0x74