vkms_vblank_simulate: vblank timer overrun
=============================
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
9 locks held by syz-executor/7760:
#0: ffffffff8c1a68f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
#0: ffffffff8c1a68f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
#0: ffffffff8c1a68f0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x21f/0x1380 kernel/fork.c:1518
#1: ffff88801686c028 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88801686c028 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
#1: ffff88801686c028 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#1: ffff88801686c028 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x238/0x1380 kernel/fork.c:1518
#2: ffff888075862428 (&mm->mmap_lock/1){+.+.}-{3:3}, at: mmap_write_lock_nested include/linux/mmap_lock.h:78 [inline]
#2: ffff888075862428 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mmap kernel/fork.c:513 [inline]
#2: ffff888075862428 (&mm->mmap_lock/1){+.+.}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#2: ffff888075862428 (&mm->mmap_lock/1){+.+.}-{3:3}, at: copy_mm+0x354/0x1380 kernel/fork.c:1518
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1032 [inline]
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1167 [inline]
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1204 [inline]
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1228 [inline]
#3: ffff88806284dc18 (ptlock_ptr(page)#2){+.+.}-{2:2}, at: copy_page_range+0xeb3/0x3220 mm/memory.c:1301
#4: ffff888059295078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pte_range mm/memory.c:1039 [inline]
#4: ffff888059295078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pmd_range mm/memory.c:1167 [inline]
#4: ffff888059295078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_pud_range mm/memory.c:1204 [inline]
#4: ffff888059295078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_p4d_range mm/memory.c:1228 [inline]
#4: ffff888059295078 (ptlock_ptr(page)#2/1){+.+.}-{2:2}, at: copy_page_range+0xfbf/0x3220 mm/memory.c:1301
#5: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:313
#6: ffff888025add148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: net_tx_action+0x6bc/0x870 net/core/dev.c:5128
#7: ffff888025add108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:364 [inline]
#7: ffff888025add108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
#8: ffffffff8c11c760 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:312
stack backtrace:
CPU: 0 PID: 7760 Comm: syz-executor 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
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:PageSwapBacked include/linux/page-flags.h:371 [inline]
RIP: 0010:mm_counter_file include/linux/mm.h:1977 [inline]
RIP: 0010:mm_counter include/linux/mm.h:1986 [inline]
RIP: 0010:copy_present_pte mm/memory.c:967 [inline]
RIP: 0010:copy_pte_range mm/memory.c:1081 [inline]
RIP: 0010:copy_pmd_range mm/memory.c:1167 [inline]
RIP: 0010:copy_pud_range mm/memory.c:1204 [inline]
RIP: 0010:copy_p4d_range mm/memory.c:1228 [inline]
RIP: 0010:copy_page_range+0x1754/0x3220 mm/memory.c:1301
Code: 00 74 08 48 89 df e8 5b ad 10 00 4c 8b 3b 44 89 fb 83 e3 01 31 ff 48 89 de e8 08 49 cc ff 49 83 fe ff 4c 8b ac 24 b8 00 00 00 <0f> 84 bb 18 00 00 48 85 db 0f 85 18 08 00 00 e8 08 45 cc ff 48 8b
RSP: 0018:ffffc90002f5f6a0 EFLAGS: 00000213
RAX: ffffffff81ab86e8 RBX: 0000000000000000 RCX: ffff8880260a5940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002f5f950 R08: dffffc0000000000 R09: fffff94000288e37
R10: fffff94000288e37 R11: 1ffffd4000288e36 R12: 00007f49df8e6000
R13: 80000000511c6007 R14: 00fff0000000000a R15: 0000000000000000
dup_mmap kernel/fork.c:615 [inline]
dup_mm kernel/fork.c:1466 [inline]
copy_mm+0xc60/0x1380 kernel/fork.c:1518
copy_process+0x17c6/0x3e00 kernel/fork.c:2290
kernel_clone+0x219/0x930 kernel/fork.c:2679
__do_sys_clone kernel/fork.c:2796 [inline]
__se_sys_clone kernel/fork.c:2780 [inline]
__x64_sys_clone+0x170/0x1c0 kernel/fork.c:2780
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: 0033:0x7f49e062b713
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffcc7238188 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f49e062b713
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 000055555f8167d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 00000000000633fc R15: 00007ffcc7238320
vkms_vblank_simulate: vblank timer overrun
----------------
Code disassembly (best guess):
0: 00 74 08 48 add %dh,0x48(%rax,%rcx,1)
4: 89 df mov %ebx,%edi
6: e8 5b ad 10 00 call 0x10ad66
b: 4c 8b 3b mov (%rbx),%r15
e: 44 89 fb mov %r15d,%ebx
11: 83 e3 01 and $0x1,%ebx
14: 31 ff xor %edi,%edi
16: 48 89 de mov %rbx,%rsi
19: e8 08 49 cc ff call 0xffcc4926
1e: 49 83 fe ff cmp $0xffffffffffffffff,%r14
22: 4c 8b ac 24 b8 00 00 mov 0xb8(%rsp),%r13
29: 00
* 2a: 0f 84 bb 18 00 00 je 0x18eb <-- trapping instruction
30: 48 85 db test %rbx,%rbx
33: 0f 85 18 08 00 00 jne 0x851
39: e8 08 45 cc ff call 0xffcc4546
3e: 48 rex.W
3f: 8b .byte 0x8b