[v5.15] INFO: rcu detected stall in mmap_file (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dc027a595035 Linux 5.15.209
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17c068ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=bde8280833fcc88121dd
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/3d51783ddbbf/disk-dc027a59.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b6879bfcdc05/vmlinux-dc027a59.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e4755824edc0/bzImage-dc027a59.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bde828...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (1 ticks this GP) idle=3b3/1/0x4000000000000002 softirq=10176/10176 fqs=1
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P144/1:b..l
(detected by 1, t=10502 jiffies, g=11473, q=109)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 5806 Comm: syz.2.391 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__lock_acquire+0x1d1/0x7d10 kernel/locking/lockdep.c:4915
Code: 0f 85 2d 65 00 00 45 8b 26 48 c7 c0 80 ef 2d 96 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85 3a 65 00 00 83 3d 51 c3 d0 14 00 75 0a <41> 83 fc 30 0f 83 11 58 00 00 4c 89 6c 24 30 44 8b 6d 20 48 c7 c0
RSP: 0018:ffffc90000006c40 EFLAGS: 00000046
RAX: 0000000000000004 RBX: ffffffff8c31f360 RCX: ffffffff962def03
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8c31f360
RBP: ffffc90000006e90 R08: dffffc0000000000 R09: 0000000000000001
R10: dffffc0000000000 R11: fffffbfff1b140de R12: 0000000000000005
R13: ffff888028d01dc0 R14: ffff888028d028a8 R15: ffffffff8fb60f40
FS: 000055556807e500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000011 CR3: 0000000053cee000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
__perf_output_begin kernel/events/ring_buffer.c:163 [inline]
perf_output_begin_forward+0xa5/0xa40 kernel/events/ring_buffer.c:271
__perf_event_output kernel/events/core.c:7804 [inline]
perf_event_output_forward+0x19b/0x2e0 kernel/events/core.c:7822
__perf_event_overflow+0x364/0x530 kernel/events/core.c:9515
perf_tp_event+0x383/0xbf0 kernel/events/core.c:10047
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 f2 cc 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007780 EFLAGS: 00000206
RAX: 29e3ee9cdb514e00 RBX: 1ffff92000000ef4 RCX: 29e3ee9cdb514e00
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: ffffffff8a7a09c0
RBP: ffffc90000007860 R08: ffffffff901d818f R09: 1ffffffff203b031
R10: dffffc0000000000 R11: fffffbfff203b032 R12: ffffffff8c323800
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock include/linux/rcupdate.h:772 [inline]
__ip_queue_xmit+0x1242/0x1c00 net/ipv4/ip_output.c:539
__tcp_transmit_skb+0x1d11/0x3200 net/ipv4/tcp_output.c:1404
tcp_delack_timer_handler+0x32e/0x730 net/ipv4/tcp_timer.c:314
tcp_delack_timer+0x188/0x2e0 net/ipv4/tcp_timer.c:341
call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648
expire_timers kernel/time/timer.c:1699 [inline]
__run_timers+0x53e/0x800 kernel/time/timer.c:1970
run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983
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
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 4f 9d 8b f7 65 8b 05 70 86 3b 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900032bf980 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a06 RCX: 29e3ee9cdb514e00
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: 0000000000000001
RBP: ffffc900032bfa10 R08: ffffffff901d80f7 R09: 1ffffffff203b01e
R10: dffffc0000000000 R11: fffffbfff203b01f R12: dffffc0000000000
R13: ffffc9000f3fe000 R14: ffffffff964c0ef0 R15: 1ffff92000657f30
__debug_check_no_obj_freed lib/debugobjects.c:982 [inline]
debug_check_no_obj_freed+0x515/0x530 lib/debugobjects.c:1003
__vunmap+0x27e/0xa50 mm/vmalloc.c:2614
kcov_mmap+0x89/0x120 kernel/kcov.c:498
call_mmap include/linux/fs.h:2178 [inline]
mmap_file+0x5d/0xb0 mm/util.c:1092
__mmap_region mm/mmap.c:1796 [inline]
mmap_region+0xf88/0x1650 mm/mmap.c:2933
do_mmap+0x819/0xe90 mm/mmap.c:1586
vm_mmap_pgoff+0x1c1/0x2d0 mm/util.c:551
ksys_mmap_pgoff+0x54b/0x790 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: 0033:0x7f8443094bc2
Code: 4f 01 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 6e 5b 5d c3 0f 1f 00 48 c7 c0 e8 ff ff ff 64
RSP: 002b:00007ffc3bcbeab8 EFLAGS: 00000206 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f8440e8b000 RCX: 00007f8443094bc2
RDX: 0000000000000003 RSI: 0000000000400000 RDI: 00007f8440e8b000
RBP: 0000000000000011 R08: 00000000000000db R09: 0000000000000000
R10: 0000000000000011 R11: 0000000000000206 R12: 0000000000000003
R13: 0000000000000001 R14: 0000000000000000 R15: 00007f844330dfa0
</TASK>
task:kworker/u4:1 state:R running task stack:24880 pid: 144 ppid: 2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
preempt_schedule_notrace+0xd9/0x120 kernel/sched/core.c:6650
preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
trace_lock_acquire include/trace/events/lock.h:13 [inline]
lock_acquire+0x3ed/0x400 kernel/locking/lockdep.c:5594
rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
rcu_read_lock include/linux/rcupdate.h:740 [inline]
inet_twsk_purge+0x119/0x840 net/ipv4/inet_timewait_sock.c:268
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x791/0xba0 net/core/net_namespace.c:635
process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g11473 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=1 timer-softirq=5305
rcu: rcu_preempt kthread starved for 10500 jiffies! g11473 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
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:I stack:27664 pid: 15 ppid: 2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
NMI backtrace for cpu 1
CPU: 1 PID: 4172 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
<IRQ>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
rcu_check_gp_kthread_starvation+0x1cd/0x250 kernel/rcu/tree_stall.h:487
print_other_cpu_stall+0x1110/0x1270 kernel/rcu/tree_stall.h:592
check_cpu_stall kernel/rcu/tree_stall.h:745 [inline]
rcu_pending kernel/rcu/tree.c:3936 [inline]
rcu_sched_clock_irq+0x843/0x1120 kernel/rcu/tree.c:2619
update_process_times+0x193/0x200 kernel/time/timer.c:2021
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x4b4/0xb70 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
__sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0x9b/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x159/0x1b0 arch/x86/kernel/kvm.c:918
Code: 89 df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 4b 0f b6 1f e8 f7 bb 4a 00 44 38 e3 75 10 66 90 0f 00 2d b9 cc f3 08 fb f4 <e9> 16 ff ff ff fb e9 10 ff ff ff e8 a7 c0 88 08 89 f9 80 e1 07 38
RSP: 0018:ffffc900011df8c0 EFLAGS: 00000246
RAX: 5546974b8dcc5800 RBX: 0000000000000003 RCX: 5546974b8dcc5800
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: ffffffff8a7a09c0
RBP: ffffc900011df970 R08: ffffffff901d818f R09: 1ffffffff203b031
R10: dffffc0000000000 R11: fffffbfff203b032 R12: 0000000000000003
R13: ffff8880b913b154 R14: dffffc0000000000 R15: 1ffff9200023bf18
pv_wait arch/x86/include/asm/paravirt.h:597 [inline]
pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
__pv_queued_spin_lock_slowpath+0x60f/0x9c0 kernel/locking/qspinlock.c:508
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
do_raw_spin_lock+0x265/0x2f0 kernel/locking/spinlock_debug.c:115
spin_lock_bh include/linux/spinlock.h:369 [inline]
lock_sock_nested+0x68/0x100 net/core/sock.c:3262
lock_sock include/net/sock.h:1744 [inline]
tcp_sendmsg+0x1d/0x40 net/ipv4/tcp.c:1459
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1089
call_write_iter include/linux/fs.h:2173 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x745/0xd60 fs/read_write.c:594
ksys_write+0x152/0x260 fs/read_write.c:647
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: 0033:0x7f6ae195afd7
Code: 48 89 fa 4c 89 df e8 a8 56 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd75321e30 EFLAGS: 00000202 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000055556c665500 RCX: 00007f6ae195afd7
RDX: 0000000000000140 RSI: 00007f6adb042ec0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000140
R13: 000055556c679fb0 R14: 00007ffd753223d0 R15: 00007f6adb042ec0
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup