[v6.1] INFO: rcu detected stall in kcov_ioctl (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7c87defbd336 Linux 6.1.169
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11bd5702580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f0605c5af04d7603
dashboard link: https://syzkaller.appspot.com/bug?extid=80d0bce16c3a58d76bb3
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8d71e14f22ca/disk-7c87defb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/49c26e1231bb/vmlinux-7c87defb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bac8352e3eab/bzImage-7c87defb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80d0bc...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P9998/1:b..l
(detected by 1, t=10503 jiffies, g=73621, q=326 ncpus=2)
task:syz-executor state:R running task stack:24816 pid:9998 ppid:4254 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6874
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:rcu_read_unlock include/linux/rcupdate.h:820 [inline]
RIP: 0010:page_ext_put+0x12/0xb0 mm/page_ext.c:182
Code: d4 b9 a4 ff e9 d9 fe ff ff e8 ca b9 a4 ff 0f 0b e9 0a ff ff ff 0f 1f 00 53 48 89 fb e8 b7 b9 a4 ff 48 85 db 0f 84 93 00 00 00 <e8> 09 40 50 08 89 c3 31 ff 89 c6 e8 fe bc a4 ff 85 db 74 10 e8 15
RSP: 0018:ffffc900038bf9d0 EFLAGS: 00000286
RAX: ffffffff81ddbb99 RBX: ffff88801b5bcf00 RCX: ffff8880537c0000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff88801b5bcf00
RBP: 0000000000102dc2 R08: ffff88801b5bcf07 R09: 1ffff110036b79e0
R10: dffffc0000000000 R11: ffffed10036b79e1 R12: 0000000000000001
R13: 0000000000000000 R14: ffffea000178b800 R15: 0000000000000001
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2559
prep_new_page mm/page_alloc.c:2566 [inline]
get_page_from_freelist+0x1a1e/0x1ab0 mm/page_alloc.c:4357
__alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5657
vm_area_alloc_pages mm/vmalloc.c:3002 [inline]
__vmalloc_area_node mm/vmalloc.c:3071 [inline]
__vmalloc_node_range+0x944/0x13b0 mm/vmalloc.c:3243
vmalloc_user+0x70/0x80 mm/vmalloc.c:3397
kcov_ioctl+0x54/0x620 kernel/kcov.c:713
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3aff39c4ab
RSP: 002b:00007ffecb08f9f0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000080000 RCX: 00007f3aff39c4ab
RDX: 0000000000080000 RSI: ffffffff80086301 RDI: 00000000000000d8
RBP: 00007f3aff616038 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000003 R14: 00007ffecb08fca8 R15: 0000000000000000
</TASK>
rcu: rcu_preempt kthread starved for 10464 jiffies! g73621 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:26416 pid:16 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x11d1/0x40e0 kernel/sched/core.c:6562
schedule+0xb9/0x180 kernel/sched/core.c:6638
schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x303/0x1340 kernel/rcu/tree.c:1706
rcu_gp_kthread+0x99/0x3b0 kernel/rcu/tree.c:1905
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:741
vkms_vblank_simulate: vblank timer overrun


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