[v6.1] INFO: rcu detected stall in sys_unshare

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c6114c845984 Linux 6.1.65
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11b31c86e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=61e0c4a5fbb36a13
dashboard link: https://syzkaller.appspot.com/bug?extid=bdc8340e3db76c2af2cc
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1565a21ce80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16e62354e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f761cbc53791/disk-c6114c84.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d6a6e4496af6/vmlinux-c6114c84.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f4794a58f735/bzImage-c6114c84.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bdc834...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P3576/1:b..l
(detected by 1, t=10503 jiffies, g=5981, q=21 ncpus=2)
task:syz-executor524 state:R running task stack:24984 pid:3576 ppid:3570 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x142d/0x4550 kernel/sched/core.c:6558
preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6870
irqentry_exit+0x53/0x80 kernel/entry/common.c:433
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0010:packet_notifier+0x12c/0xa30 net/packet/af_packet.c:4151
Code: c2 80 15 f0 8b e8 74 04 05 f8 48 81 c3 b8 03 00 00 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 c7 4b 7c f8 4c 8b 3b <4d> 85 ff 0f 84 3b 08 00 00 49 83 c7 98 0f 84 31 08 00 00 48 8b 44
RSP: 0018:ffffc90003c3f7f8 EFLAGS: 00000246
RAX: 1ffff1100e685b0f RBX: ffff88807342d878 RCX: ffff8880767d1dc0
RDX: 0000000000000000 RSI: ffffffff8b3cf3a0 RDI: ffffffff8b3cf360
RBP: 0000000000000001 R08: ffffffff8965a382 R09: fffffbfff2091c45
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: dffffc0000000000 R14: 0000000000000005 R15: 0000000000000000
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xd0/0x170 kernel/notifier.c:455
call_netdevice_notifiers_info net/core/dev.c:1970 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2008 [inline]
call_netdevice_notifiers+0x145/0x1b0 net/core/dev.c:2022
register_netdevice+0x12f2/0x1720 net/core/dev.c:10126
register_netdev+0x37/0x50 net/core/dev.c:10219
ip6gre_init_net+0x211/0x2e0 net/ipv6/ip6_gre.c:1644
ops_init+0x356/0x600 net/core/net_namespace.c:135
setup_net+0x4b5/0xb90 net/core/net_namespace.c:332
copy_net_ns+0x395/0x5d0 net/core/net_namespace.c:478
create_new_namespaces+0x425/0x7a0 kernel/nsproxy.c:110
unshare_nsproxy_namespaces+0x11e/0x170 kernel/nsproxy.c:226
ksys_unshare+0x580/0xb20 kernel/fork.c:3203
__do_sys_unshare kernel/fork.c:3274 [inline]
__se_sys_unshare kernel/fork.c:3272 [inline]
__x64_sys_unshare+0x34/0x40 kernel/fork.c:3272
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f22996822f7
RSP: 002b:00007ffe03626f38 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007ffe03626f68 RCX: 00007f22996822f7
RDX: 00007f2299680e79 RSI: 00007ffe03626fe0 RDI: 0000000040000000
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000555555d7d370
R13: 0000000000000003 R14: 0000000000000003 R15: 00007ffe03626fa0
</TASK>
rcu: rcu_preempt kthread starved for 10537 jiffies! g5981 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R running task stack:27032 pid:16 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5245 [inline]
__schedule+0x142d/0x4550 kernel/sched/core.c:6558
schedule+0xbf/0x180 kernel/sched/core.c:6634
schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1935
rcu_gp_fqs_loop+0x2d2/0x1120 kernel/rcu/tree.c:1674
rcu_gp_kthread+0xa3/0x3a0 kernel/rcu/tree.c:1873
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 3600 Comm: syz-executor524 Not tainted 6.1.65-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
RIP: 0010:xsave_to_user_sigframe arch/x86/kernel/fpu/xstate.h:279 [inline]
RIP: 0010:copy_fpregs_to_sigframe arch/x86/kernel/fpu/signal.c:162 [inline]
RIP: 0010:copy_fpstate_to_sigframe+0x51e/0xda0 arch/x86/kernel/fpu/signal.c:231
Code: 57 00 4c 89 e3 48 c1 eb 20 4c 89 ff 4c 89 e6 31 d2 e8 56 46 00 00 0f 01 cb 4c 8b 7c 24 20 4c 89 ff 44 89 e0 89 da 48 0f ae 27 <31> c0 89 c3 0f 01 ca 48 8b 44 24 30 42 0f b6 04 28 84 c0 0f 85 c9
RSP: 0018:ffffc90003cff980 EFLAGS: 00040286
RAX: 0000000000000007 RBX: 0000000000000000 RCX: ffff888077343b80
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffe03626b40
RBP: ffffc90003cffb50 R08: ffffffff8132fe70 R09: ffffed100ee68771
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000007
R13: dffffc0000000000 R14: ffff888077343b80 R15: 00007ffe03626b40
FS: 0000555555d7d3c0(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000140 CR3: 0000000029cfc000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
</IRQ>
<TASK>
get_sigframe+0x378/0x4b0 arch/x86/kernel/signal.c:297
__setup_rt_frame arch/x86/kernel/signal.c:472 [inline]
setup_rt_frame arch/x86/kernel/signal.c:784 [inline]
handle_signal arch/x86/kernel/signal.c:828 [inline]
arch_do_signal_or_restart+0x4ef/0x1a10 arch/x86/kernel/signal.c:873
exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:168
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:204
__syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:297
do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f2299680e79
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 18 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe03626f38 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f2299680e79
RDX: 0000000020000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000000f4240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000555555d7d370
R13: 0000000000000000 R14: 00007ffe03626fb0 R15: 00007ffe03626fa0
</TASK>
sched: RT throttling activated


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