INFO: rcu detected stall in dev_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f6d5cb9e Linux 4.19.142
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=112fea15900000
kernel config: https://syzkaller.appspot.com/x/.config?x=30067df04d3254aa
dashboard link: https://syzkaller.appspot.com/bug?extid=25860d918eed840a03e1
compiler: gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+25860d...@syzkaller.appspotmail.com

batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-...!: (1 GPs behind) idle=c8a/1/0x4000000000000002 softirq=129733/129736 fqs=26
rcu: (t=10502 jiffies g=166693 q=1032)
rcu: rcu_preempt kthread starved for 10450 jiffies! g166693 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt I29208 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_timeout+0x4cf/0xfe0 kernel/time/timer.c:1825
rcu_gp_kthread+0xdad/0x21c0 kernel/rcu/tree.c:2202
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
NMI backtrace for cpu 0
CPU: 0 PID: 17337 Comm: syz-executor.4 Not tainted 4.19.142-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1eb lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
rcu_dump_cpu_stacks+0x15f/0x19c kernel/rcu/tree.c:1340
print_cpu_stall kernel/rcu/tree.c:1478 [inline]
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3293 [inline]
rcu_pending kernel/rcu/tree.c:3336 [inline]
rcu_check_callbacks.cold+0x62d/0xe19 kernel/rcu/tree.c:2682
update_process_times+0x2a/0xb0 kernel/time/timer.c:1650
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:168
tick_sched_timer+0xfc/0x290 kernel/time/tick-sched.c:1278
__run_hrtimer kernel/time/hrtimer.c:1401 [inline]
__hrtimer_run_queues+0x3f6/0xe60 kernel/time/hrtimer.c:1463
hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1521
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline]
smp_apic_timer_interrupt+0x10c/0x550 arch/x86/kernel/apic/apic.c:1092
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline]
RIP: 0010:lock_acquire+0x1ec/0x3c0 kernel/locking/lockdep.c:3910
Code: 08 00 00 00 00 00 00 48 c1 e8 03 80 3c 10 00 0f 85 b7 01 00 00 48 83 3d d9 c7 80 07 00 0f 84 2a 01 00 00 48 8b 7c 24 08 57 9d <0f> 1f 44 00 00 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f c3 65 8b
RSP: 0018:ffff88820cf87688 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a4b69 RBX: ffff888094d781c0 RCX: 0000000000001dc9
RDX: dffffc0000000000 RSI: 00000000d699bbe2 RDI: 0000000000000282
RBP: ffff888081e46748 R08: ffffffff8b3f96c8 R09: 0000000000000002
R10: ffff888094d78a98 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000001
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:168
spin_lock_bh include/linux/spinlock.h:334 [inline]
batadv_tt_local_purge+0x11b/0x370 net/batman-adv/translation-table.c:1452
batadv_tt_local_resize_to_mtu+0x8e/0x130 net/batman-adv/translation-table.c:4205
batadv_update_min_mtu net/batman-adv/hard-interface.c:637 [inline]
batadv_hard_if_event+0xbb3/0x15c0 net/batman-adv/hard-interface.c:1059
notifier_call_chain+0xc0/0x230 kernel/notifier.c:93
call_netdevice_notifiers_mtu net/core/dev.c:1785 [inline]
dev_set_mtu_ext+0x384/0x580 net/core/dev.c:7810
dev_set_mtu+0x95/0x120 net/core/dev.c:7831
dev_ifsioc+0x30a/0x8c0 net/core/dev_ioctl.c:244
dev_ioctl+0x1ab/0xc4c net/core/dev_ioctl.c:488
sock_do_ioctl+0x148/0x2d0 net/socket.c:973
sock_ioctl+0x2ef/0x5d0 net/socket.c:1074
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
__do_sys_ioctl fs/ioctl.c:712 [inline]
__se_sys_ioctl fs/ioctl.c:710 [inline]
__x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45d5b9
Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbe8c28dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000001e240 RCX: 000000000045d5b9
RDX: 0000000020000040 RSI: 0000000000008922 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffe47c3e78f R14: 00007fbe8c28e9c0 R15: 000000000118cf4c
net_ratelimit: 5850 callbacks suppressed
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
net_ratelimit: 6639 callbacks suppressed
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.