[v5.15] INFO: rcu detected stall in sys_utimensat

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14af3d8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=a139b1a93fe7c028962c
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15ab78f0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14a5838c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a139b1...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P3658/1:b..l P4091/1:b..l
(detected by 0, t=10502 jiffies, g=5937, q=162)
task:udevd state:R running task stack: 0 pid: 4091 ppid: 3658 flags:0x00000004
Call trace:
__switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0xe00/0x1c0c kernel/sched/core.c:6376
preempt_schedule_irq+0x90/0x214 kernel/sched/core.c:6780
arm64_preempt_schedule_irq+0x14c/0x21c arch/arm64/kernel/entry-common.c:260
el1_interrupt+0x40/0x58 arch/arm64/kernel/entry-common.c:463
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
arch_local_irq_restore arch/arm64/include/asm/irqflags.h:122 [inline]
seqcount_lockdep_reader_access+0x214/0x2bc include/linux/seqlock.h:105
__follow_mount_rcu fs/namei.c:1457 [inline]
handle_mounts fs/namei.c:1490 [inline]
step_into+0x4cc/0xa24 fs/namei.c:1806
walk_component+0x1f0/0x3a8 fs/namei.c:1982
link_path_walk+0x590/0xb8c fs/namei.c:-1
path_lookupat+0x90/0x3d0 fs/namei.c:2454
filename_lookup+0x180/0x414 fs/namei.c:2484
user_path_at_empty+0x5c/0x1a0 fs/namei.c:2883
user_path_at include/linux/namei.h:57 [inline]
do_utimes_path fs/utimes.c:94 [inline]
do_utimes+0x130/0x288 fs/utimes.c:144
__do_sys_utimensat fs/utimes.c:163 [inline]
__se_sys_utimensat fs/utimes.c:147 [inline]
__arm64_sys_utimensat+0x144/0x210 fs/utimes.c:147
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
task:udevd state:R running task stack: 0 pid: 3658 ppid: 1 flags:0x00000004
Call trace:
__switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0xe00/0x1c0c kernel/sched/core.c:6376
preempt_schedule_common+0x138/0x218 kernel/sched/core.c:6552
preempt_schedule+0x64/0x84 kernel/sched/core.c:6577
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
_raw_spin_unlock_irqrestore+0x108/0x14c kernel/locking/spinlock.c:194
spin_unlock_irqrestore include/linux/spinlock.h:418 [inline]
__wake_up_common_lock kernel/sched/wait.c:140 [inline]
__wake_up_sync_key+0x11c/0x178 kernel/sched/wait.c:205
sock_def_readable+0x150/0x278 net/core/sock.c:3093
__netlink_sendskb net/netlink/af_netlink.c:1264 [inline]
netlink_sendskb+0xa4/0x178 net/netlink/af_netlink.c:1270
netlink_unicast+0x2d8/0x8b0 net/netlink/af_netlink.c:1359
netlink_sendmsg+0x6e8/0x9cc net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
____sys_sendmsg+0x61c/0x920 net/socket.c:2436
___sys_sendmsg+0x1d0/0x240 net/socket.c:2490
__sys_sendmsg net/socket.c:2519 [inline]
__do_sys_sendmsg net/socket.c:2528 [inline]
__se_sys_sendmsg net/socket.c:2526 [inline]
__arm64_sys_sendmsg+0x1a8/0x254 net/socket.c:2526
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
rcu: rcu_preempt kthread starved for 10506 jiffies! g5937 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: 0 pid: 15 ppid: 2 flags:0x00000008
Call trace:
__switch_to+0x2f4/0x558 arch/arm64/kernel/process.c:521
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0xe00/0x1c0c kernel/sched/core.c:6376
schedule+0x11c/0x1c8 kernel/sched/core.c:6459
schedule_timeout+0x180/0x2c8 kernel/time/timer.c:1914
rcu_gp_fqs_loop+0x25c/0x11f0 kernel/rcu/tree.c:1972
rcu_gp_kthread+0xc4/0x2a8 kernel/rcu/tree.c:2145
kthread+0x374/0x454 kernel/kthread.c:334
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855
rcu: Stack dump where RCU GP kthread last ran:
Task dump for CPU 0:
task:syz.0.16 state:R running task stack: 0 pid: 4237 ppid: 4171 flags:0x00000001
Call trace:
dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
sched_show_task+0x3c8/0x4b4 kernel/sched/core.c:8640
dump_cpu_task+0x84/0xa8 kernel/sched/core.c:10927
rcu_check_gp_kthread_starvation+0x1e8/0x274 kernel/rcu/tree_stall.h:488
print_other_cpu_stall+0x1a24/0x1c10 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+0x1558/0x1810 kernel/rcu/tree.c:2619
update_process_times+0x1c4/0x260 kernel/time/timer.c:1818
tick_sched_handle kernel/time/tick-sched.c:254 [inline]
tick_sched_timer+0x30c/0x4bc kernel/time/tick-sched.c:1473
__run_hrtimer kernel/time/hrtimer.c:1690 [inline]
__hrtimer_run_queues+0x3fc/0xb6c kernel/time/hrtimer.c:1754
hrtimer_interrupt+0x2bc/0xb5c kernel/time/hrtimer.c:1816
timer_handler drivers/clocksource/arm_arch_timer.c:659 [inline]
arch_timer_handler_virt+0x74/0x88 drivers/clocksource/arm_arch_timer.c:670
handle_percpu_devid_irq+0x29c/0x76c kernel/irq/chip.c:930
generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
handle_irq_desc kernel/irq/irqdesc.c:652 [inline]
handle_domain_irq+0x144/0x1fc kernel/irq/irqdesc.c:707
gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765
call_on_irq_stack+0x24/0x30 arch/arm64/kernel/entry.S:855
do_interrupt_handler+0x6c/0x88 arch/arm64/kernel/entry-common.c:267
el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454
el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470
el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522
arch_local_irq_restore+0x8/0x10 arch/arm64/include/asm/irqflags.h:122
lock_is_held include/linux/lockdep.h:287 [inline]
___might_sleep+0x98/0x4d4 kernel/sched/core.c:9605
__might_sleep+0x98/0x124 kernel/sched/core.c:9593
__might_fault+0x80/0x128 mm/memory.c:5354
setup_sigframe arch/arm64/kernel/signal.c:630 [inline]
setup_rt_frame arch/arm64/kernel/signal.c:792 [inline]
handle_signal arch/arm64/kernel/signal.c:833 [inline]
do_signal arch/arm64/kernel/signal.c:908 [inline]
do_notify_resume+0xcbc/0x3128 arch/arm64/kernel/signal.c:946
prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584


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