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INFO: rcu detected stall in sys_unshare

Status: upstream: reported on 2025/07/18 06:21
Reported-by: syzbot+a3cc5c92f0cb30fcda0e@syzkaller.appspotmail.com
First crash: 35d, last: 35d
▶ ▼ Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_unshare (2) mm 1 1 2053d 2053d 0/29 closed as invalid on 2020/01/08 05:23
upstream INFO: rcu detected stall in sys_unshare (5) net 1 1 1315d 1315d 0/29 closed as invalid on 2022/02/08 10:10
upstream INFO: rcu detected stall in sys_unshare (3) net 1 1 1539d 1539d 0/29 auto-closed as invalid on 2021/09/03 04:28
linux-5.15 INFO: rcu detected stall in sys_unshare missing-backport origin:upstream 1 C done 9 16d 458d 0/3 upstream: reported C repro on 2024/05/20 16:51
upstream INFO: rcu detected stall in sys_unshare (6) kernfs 1 1 1285d 1285d 0/29 auto-closed as invalid on 2022/05/15 15:21
upstream INFO: rcu detected stall in sys_unshare (9) mm kernfs 1 C inconclusive done 53 9d16h 650d 0/29 upstream: reported C repro on 2023/11/11 00:17
upstream INFO: rcu detected stall in sys_unshare mm 1 3 2089d 2089d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in sys_unshare (4) kernel 1 1 1448d 1448d 0/29 auto-closed as invalid on 2021/12/03 09:38
upstream INFO: rcu detected stall in sys_unshare (7) bpf net 1 12 901d 1032d 0/29 auto-obsoleted due to no activity on 2023/06/03 15:22
linux-6.1 INFO: rcu detected stall in sys_unshare origin:upstream missing-backport 1 C error 5 350d 627d 0/3 upstream: reported C repro on 2023/12/04 08:29
android-5-15 BUG: soft lockup in sys_unshare 1 1 474d 474d 0/2 auto-obsoleted due to no activity on 2024/08/03 08:28

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=cf1c/1/0x4000000000000000 softirq=46065/46065 fqs=0
rcu: 	(detected by 1, t=10506 jiffies, g=56021, q=519 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 11189 Comm: syz-executor Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:rb_erase_cached include/linux/rbtree.h:123 [inline]
RIP: 0010:timerqueue_del+0x5a/0x100 lib/timerqueue.c:57
Code: 74 08 4c 89 f7 e8 66 20 7f f7 4d 8b 3e 4c 89 ff 4c 89 f6 e8 d8 dc 27 f7 4d 39 f7 0f 84 98 00 00 00 e8 ba da 27 f7 4c 8d 63 08 <4d> 89 e7 49 c1 ef 03 43 80 3c 2f 00 74 08 4c 89 e7 e8 30 20 7f f7
RSP: 0018:ffffc90000007d08 EFLAGS: 00000006
RAX: ffffffff8a5dbb76 RBX: ffff8880b8e2ba90 RCX: ffff888027d61e00
RDX: 0000000000010000 RSI: ffff88802a514340 RDI: 0000000000000001
RBP: 1ffff110054a2868 R08: ffffffff8e4a7cef R09: 1ffffffff1c94f9d
R10: dffffc0000000000 R11: fffffbfff1c94f9e R12: ffff8880b8e2ba98
R13: dffffc0000000000 R14: ffff88802a514340 R15: 0000000000000001
FS:  0000555593b21500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000040 CR3: 000000004b1df000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 __remove_hrtimer kernel/time/hrtimer.c:1146 [inline]
 __run_hrtimer kernel/time/hrtimer.c:1735 [inline]
 __hrtimer_run_queues+0x374/0xc40 kernel/time/hrtimer.c:1819
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1881
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_release+0x11c/0x8b0 kernel/locking/lockdep.c:5767
Code: 7d 04 00 00 65 4c 8b 35 82 2e 9c 7e 49 8d 9e dc 0a 00 00 48 89 d8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 20 05 00 00 83 3b 00 <0f> 85 51 04 00 00 4c 89 74 24 10 48 c7 84 24 a0 00 00 00 00 00 00
RSP: 0018:ffffc900030d7060 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888027d628dc RCX: e681869359b0e200
RDX: 0000000000000000 RSI: ffffffff8afc6660 RDI: ffffffff8afc6620
RBP: ffffc900030d7178 R08: ffffffff8e4a7cef R09: 1ffffffff1c94f9d
R10: dffffc0000000000 R11: fffffbfff1c94f9e R12: ffffffff8192c2c6
R13: dffffc0000000000 R14: ffff888027d61e00 R15: 1ffff9200061ae18
 rcu_lock_release include/linux/rcupdate.h:344 [inline]
 rcu_read_unlock include/linux/rcupdate.h:819 [inline]
 is_bpf_text_address+0x28f/0x2a0 kernel/bpf/core.c:743
 kernel_text_address+0xa0/0xd0 kernel/extable.c:125
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb2/0x230 mm/slab_common.c:1027
 kmemdup+0x2b/0x70 mm/util.c:131
 kmemdup include/linux/fortify-string.h:779 [inline]
 mpls_dev_sysctl_register+0xb9/0x2e0 net/mpls/af_mpls.c:1391
 mpls_add_dev net/mpls/af_mpls.c:1462 [inline]
 mpls_dev_notify+0x357/0x7a0 net/mpls/af_mpls.c:1602
 notifier_call_chain+0x197/0x390 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2064 [inline]
 call_netdevice_notifiers net/core/dev.c:2078 [inline]
 register_netdevice+0x160c/0x1ae0 net/core/dev.c:10301
 __ip_tunnel_create+0x3b4/0x4c0 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x2c3/0x770 net/ipv4/ip_tunnel.c:1118
 ops_init+0x397/0x640 net/core/net_namespace.c:139
 setup_net+0x3a5/0xa00 net/core/net_namespace.c:343
 copy_net_ns+0x36d/0x5e0 net/core/net_namespace.c:520
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:228
 ksys_unshare+0x4c0/0x890 kernel/fork.c:3439
 __do_sys_unshare kernel/fork.c:3510 [inline]
 __se_sys_unshare kernel/fork.c:3508 [inline]
 __x64_sys_unshare+0x38/0x40 kernel/fork.c:3508
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa2953901a7
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffedf488d48 EFLAGS: 00000206 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007fa2955b5f40 RCX: 00007fa2953901a7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007fa2955b6738 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10505 jiffies! g56021 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=0 timer-softirq=27000
rcu: rcu_preempt kthread starved for 10506 jiffies! g56021 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:27496 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 11189 Comm: syz-executor Not tainted 6.6.99-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:trace_lock_release include/trace/events/lock.h:69 [inline]
RIP: 0010:lock_release+0xb3/0x8b0 kernel/locking/lockdep.c:5765
Code: 9c 7e 83 f8 08 0f 83 24 05 00 00 89 c3 c1 e8 06 48 8d 3c c5 e8 7c 4a 8e be 08 00 00 00 e8 55 52 75 00 48 0f a3 1d b5 f1 e2 0c <73> 0d e8 26 15 08 00 84 c0 0f 84 2c 05 00 00 48 c7 c0 9c b1 4a 8e
RSP: 0018:ffffc90000007ae0 EFLAGS: 00000057
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff81678b2b
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff8e4a7ce8
RBP: ffffc90000007bf0 R08: ffffffff8e4a7cef R09: 1ffffffff1c94f9d
R10: dffffc0000000000 R11: fffffbfff1c94f9e R12: ffffffff84254687
R13: dffffc0000000000 R14: ffffffff97104d90 R15: 1ffff92000000f68
FS:  0000555593b21500(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000000040 CR3: 000000004b1df000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
 _raw_spin_unlock_irqrestore+0x71/0x110 kernel/locking/spinlock.c:194
 debug_object_activate+0x2f7/0x4b0 lib/debugobjects.c:727
 debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
 debug_activate kernel/time/hrtimer.c:505 [inline]
 enqueue_hrtimer+0x30/0x370 kernel/time/hrtimer.c:1113
 __run_hrtimer kernel/time/hrtimer.c:1772 [inline]
 __hrtimer_run_queues+0x637/0xc40 kernel/time/hrtimer.c:1819
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1881
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_release+0x11c/0x8b0 kernel/locking/lockdep.c:5767
Code: 7d 04 00 00 65 4c 8b 35 82 2e 9c 7e 49 8d 9e dc 0a 00 00 48 89 d8 48 c1 e8 03 42 0f b6 04 28 84 c0 0f 85 20 05 00 00 83 3b 00 <0f> 85 51 04 00 00 4c 89 74 24 10 48 c7 84 24 a0 00 00 00 00 00 00
RSP: 0018:ffffc900030d7060 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888027d628dc RCX: e681869359b0e200
RDX: 0000000000000000 RSI: ffffffff8afc6660 RDI: ffffffff8afc6620
RBP: ffffc900030d7178 R08: ffffffff8e4a7cef R09: 1ffffffff1c94f9d
R10: dffffc0000000000 R11: fffffbfff1c94f9e R12: ffffffff8192c2c6
R13: dffffc0000000000 R14: ffff888027d61e00 R15: 1ffff9200061ae18
 rcu_lock_release include/linux/rcupdate.h:344 [inline]
 rcu_read_unlock include/linux/rcupdate.h:819 [inline]
 is_bpf_text_address+0x28f/0x2a0 kernel/bpf/core.c:743
 kernel_text_address+0xa0/0xd0 kernel/extable.c:125
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:198 [inline]
 __do_kmalloc_node mm/slab_common.c:1007 [inline]
 __kmalloc_node_track_caller+0xb2/0x230 mm/slab_common.c:1027
 kmemdup+0x2b/0x70 mm/util.c:131
 kmemdup include/linux/fortify-string.h:779 [inline]
 mpls_dev_sysctl_register+0xb9/0x2e0 net/mpls/af_mpls.c:1391
 mpls_add_dev net/mpls/af_mpls.c:1462 [inline]
 mpls_dev_notify+0x357/0x7a0 net/mpls/af_mpls.c:1602
 notifier_call_chain+0x197/0x390 kernel/notifier.c:93
 call_netdevice_notifiers_extack net/core/dev.c:2064 [inline]
 call_netdevice_notifiers net/core/dev.c:2078 [inline]
 register_netdevice+0x160c/0x1ae0 net/core/dev.c:10301
 __ip_tunnel_create+0x3b4/0x4c0 net/ipv4/ip_tunnel.c:267
 ip_tunnel_init_net+0x2c3/0x770 net/ipv4/ip_tunnel.c:1118
 ops_init+0x397/0x640 net/core/net_namespace.c:139
 setup_net+0x3a5/0xa00 net/core/net_namespace.c:343
 copy_net_ns+0x36d/0x5e0 net/core/net_namespace.c:520
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11a/0x160 kernel/nsproxy.c:228
 ksys_unshare+0x4c0/0x890 kernel/fork.c:3439
 __do_sys_unshare kernel/fork.c:3510 [inline]
 __se_sys_unshare kernel/fork.c:3508 [inline]
 __x64_sys_unshare+0x38/0x40 kernel/fork.c:3508
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fa2953901a7
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffedf488d48 EFLAGS: 00000206 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007fa2955b5f40 RCX: 00007fa2953901a7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040000000
RBP: 00007fa2955b6738 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/18 06:21 linux-6.6.y d96eb99e2f0e 88248e14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_unshare
* Struck through repros no longer work on HEAD.