INFO: rcu detected stall in readlink

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
android-49	INFO: rcu detected stall in readlink	syz			1	1923d	1839d	0/3	public: reported syz repro on 2019/04/14 09:28
INFO: rcu_sched detected stalls on CPUs/tasks:
	0-...: (10501 ticks this GP) idle=c36/140000000000001/0 softirq=18127/18127 fqs=5250 
	(detected by 1, t=10502 jiffies, g=1949, c=1948, q=11)
Sending NMI from CPU 1 to CPUs 0:
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.115 msecs
NMI backtrace for cpu 0
CPU: 0 PID: 3528 Comm: udevd Not tainted 4.14.142 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888096ef64c0 task.stack: ffff888096ef8000
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:60
RSP: 0018:ffff8880aee06d68 EFLAGS: 00000212
RAX: ffff8880952d0b38 RBX: ffff8880952d0b38 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffff8880952d0bd0 RDI: ffff8880952d0b40
RBP: ffff8880aee06dc0 R08: 0000000000000000 R09: ffff888096ef6ea0
R10: ffff888096ef6e80 R11: ffff888096ef64c0 R12: dffffc0000000000
R13: ffff8880952d0940 R14: ffff8880952d0bd0 R15: ffff8880952d0bc0
FS:  00007f4a25d087a0(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4a256c5518 CR3: 0000000096e51000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 dequeue_skb net/sched/sch_generic.c:148 [inline]
 qdisc_restart net/sched/sch_generic.c:241 [inline]
 __qdisc_run+0x2b8/0xe00 net/sched/sch_generic.c:257
 __dev_xmit_skb net/core/dev.c:3235 [inline]
 __dev_queue_xmit+0x1571/0x25e0 net/core/dev.c:3493
 dev_queue_xmit+0x18/0x20 net/core/dev.c:3558
 br_dev_queue_push_xmit+0x367/0x530 net/bridge/br_forward.c:55
 br_nf_dev_queue_xmit+0x307/0x1440 net/bridge/br_netfilter_hooks.c:776
 NF_HOOK include/linux/netfilter.h:250 [inline]
 NF_HOOK include/linux/netfilter.h:244 [inline]
 br_nf_post_routing+0xb80/0xf00 net/bridge/br_netfilter_hooks.c:822
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 br_forward_finish+0x1b7/0x320 net/bridge/br_forward.c:67
 br_nf_hook_thresh+0x25b/0x2e0 net/bridge/br_netfilter_hooks.c:1005
 br_nf_forward_finish+0x264/0x640 net/bridge/br_netfilter_hooks.c:550
 NF_HOOK include/linux/netfilter.h:250 [inline]
 NF_HOOK include/linux/netfilter.h:244 [inline]
 br_nf_forward_ip net/bridge/br_netfilter_hooks.c:617 [inline]
 br_nf_forward_ip+0x5fc/0x11d0 net/bridge/br_netfilter_hooks.c:561
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 __br_forward+0x312/0x9c0 net/bridge/br_forward.c:111
 deliver_clone+0x61/0xc0 net/bridge/br_forward.c:127
 br_flood+0x43c/0x530 net/bridge/br_forward.c:222
 br_handle_frame_finish+0xaf0/0x1830 net/bridge/br_input.c:210
 br_nf_hook_thresh+0x25b/0x2e0 net/bridge/br_netfilter_hooks.c:1005
 br_nf_pre_routing_finish_ipv6+0x621/0xc50 net/bridge/br_netfilter_ipv6.c:210
 NF_HOOK include/linux/netfilter.h:250 [inline]
 br_nf_pre_routing_ipv6+0x417/0x790 net/bridge/br_netfilter_ipv6.c:240
 br_nf_pre_routing+0xdce/0x12c7 net/bridge/br_netfilter_hooks.c:491
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 br_handle_frame+0x80c/0x1110 net/bridge/br_input.c:348
 __netif_receive_skb_core+0x789/0x2ca0 net/core/dev.c:4431
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4515
 process_backlog+0x21f/0x730 net/core/dev.c:5197
 napi_poll net/core/dev.c:5598 [inline]
 net_rx_action+0x490/0xf80 net/core/dev.c:5664
 __do_softirq+0x244/0x9a0 kernel/softirq.c:288
 invoke_softirq kernel/softirq.c:368 [inline]
 irq_exit+0x160/0x1b0 kernel/softirq.c:409
 exiting_irq arch/x86/include/asm/apic.h:648 [inline]
 smp_apic_timer_interrupt+0x146/0x5e0 arch/x86/kernel/apic/apic.c:1102
 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x9/0x60 kernel/kcov.c:65
RSP: 0018:ffff888096eff888 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: ffff888096ef64c0 RBX: ffff8880a77c7ce0 RCX: 1ffffffff12391cf
RDX: 0000000000000000 RSI: ffff888096ef6d68 RDI: 0000000000000001
RBP: ffff888096eff8c8 R08: 0000000000005e26 R09: ffffffff88cae5b0
R10: ffff888096ef6d68 R11: ffff888096ef64c0 R12: 00000000000000bb
R13: ffffffff891c8e78 R14: ffff8880a77c7df0 R15: 0000000000000000
 __d_add fs/dcache.c:2620 [inline]
 d_add+0x4ff/0x640 fs/dcache.c:2653
 simple_lookup fs/libfs.c:68 [inline]
 simple_lookup+0xc5/0x110 fs/libfs.c:62
 lookup_slow+0x226/0x440 fs/namei.c:1695
 walk_component+0x698/0x1d00 fs/namei.c:1824
 lookup_last fs/namei.c:2292 [inline]
 path_lookupat.isra.0+0x1bb/0x7b0 fs/namei.c:2342
 filename_lookup+0x18e/0x380 fs/namei.c:2376
 user_path_at_empty+0x43/0x50 fs/namei.c:2630
 SYSC_readlinkat fs/stat.c:394 [inline]
 SyS_readlinkat fs/stat.c:382 [inline]
 SYSC_readlink fs/stat.c:421 [inline]
 SyS_readlink+0xb7/0x290 fs/stat.c:418
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f4a25411577
RSP: 002b:00007ffea2234af8 EFLAGS: 00000202 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 0000000001b64030 RCX: 00007f4a25411577
RDX: 00000000000003fc RSI: 00007ffea2234f24 RDI: 00007ffea2234b20
RBP: 00000000000003fc R08: 0000000001b640f0 R09: 00007f4a254661d0
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000001b7ccc0 R15: 0000000001b64030
Code: 00 00 48 c7 c7 80 99 6e 86 4c 89 35 eb 3f be 07 41 be f4 ff ff ff e8 13 3c ee ff 48 c7 05 d5 3f be 07 00 00 00 00 e9 2f ec ff ff <65> 48 8b 04 25 40 ee 01 00 48 85 c0 74 1a 65 8b 15 4b fb a4 7e 
INFO: rcu_preempt detected stalls on CPUs/tasks:
	0-...: (1 GPs behind) idle=c36/140000000000001/0 softirq=18123/18127 fqs=5248 
	(detected by 1, t=10502 jiffies, g=2727, c=2726, q=1121)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3528 Comm: udevd Not tainted 4.14.142 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888096ef64c0 task.stack: ffff888096ef8000
RIP: 0010:__list_del_entry_valid+0x89/0xf5 lib/list_debug.c:51
RSP: 0018:ffff8880aee06d48 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffff8880952d0b38 RCX: 0000000000000000
RDX: 1ffff11012a5a17a RSI: ffff8880952d0bd0 RDI: ffff8880952d0b40
RBP: ffff8880aee06d60 R08: 0000000000000000 R09: ffff888096ef6ea0
R10: ffff888096ef6e80 R11: ffff888096ef64c0 R12: ffff8880952d0bd0
R13: ffff8880952d0bd0 R14: ffff8880952d0b38 R15: ffff8880952d0bc0
FS:  00007f4a25d087a0(0000) GS:ffff8880aee00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4a256c5518 CR3: 0000000096e51000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __list_del_entry include/linux/list.h:117 [inline]
 list_move_tail include/linux/list.h:182 [inline]
 hhf_dequeue+0x57f/0xa60 net/sched/sch_hhf.c:438
 dequeue_skb net/sched/sch_generic.c:148 [inline]
 qdisc_restart net/sched/sch_generic.c:241 [inline]
 __qdisc_run+0x2b8/0xe00 net/sched/sch_generic.c:257
 __dev_xmit_skb net/core/dev.c:3235 [inline]
 __dev_queue_xmit+0x1571/0x25e0 net/core/dev.c:3493
 dev_queue_xmit+0x18/0x20 net/core/dev.c:3558
 br_dev_queue_push_xmit+0x367/0x530 net/bridge/br_forward.c:55
 br_nf_dev_queue_xmit+0x307/0x1440 net/bridge/br_netfilter_hooks.c:776
 NF_HOOK include/linux/netfilter.h:250 [inline]
 NF_HOOK include/linux/netfilter.h:244 [inline]
 br_nf_post_routing+0xb80/0xf00 net/bridge/br_netfilter_hooks.c:822
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 br_forward_finish+0x1b7/0x320 net/bridge/br_forward.c:67
 br_nf_hook_thresh+0x25b/0x2e0 net/bridge/br_netfilter_hooks.c:1005
 br_nf_forward_finish+0x264/0x640 net/bridge/br_netfilter_hooks.c:550
 NF_HOOK include/linux/netfilter.h:250 [inline]
 NF_HOOK include/linux/netfilter.h:244 [inline]
 br_nf_forward_ip net/bridge/br_netfilter_hooks.c:617 [inline]
 br_nf_forward_ip+0x5fc/0x11d0 net/bridge/br_netfilter_hooks.c:561
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 __br_forward+0x312/0x9c0 net/bridge/br_forward.c:111
 deliver_clone+0x61/0xc0 net/bridge/br_forward.c:127
 br_flood+0x43c/0x530 net/bridge/br_forward.c:222
 br_handle_frame_finish+0xaf0/0x1830 net/bridge/br_input.c:210
 br_nf_hook_thresh+0x25b/0x2e0 net/bridge/br_netfilter_hooks.c:1005
 br_nf_pre_routing_finish_ipv6+0x621/0xc50 net/bridge/br_netfilter_ipv6.c:210
 NF_HOOK include/linux/netfilter.h:250 [inline]
 br_nf_pre_routing_ipv6+0x417/0x790 net/bridge/br_netfilter_ipv6.c:240
 br_nf_pre_routing+0xdce/0x12c7 net/bridge/br_netfilter_hooks.c:491
 nf_hook_entry_hookfn include/linux/netfilter.h:108 [inline]
 nf_hook_slow+0xaf/0x1b0 net/netfilter/core.c:467
 nf_hook include/linux/netfilter.h:205 [inline]
 NF_HOOK include/linux/netfilter.h:248 [inline]
 br_handle_frame+0x80c/0x1110 net/bridge/br_input.c:348
 __netif_receive_skb_core+0x789/0x2ca0 net/core/dev.c:4431
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4515
 process_backlog+0x21f/0x730 net/core/dev.c:5197
 napi_poll net/core/dev.c:5598 [inline]
 net_rx_action+0x490/0xf80 net/core/dev.c:5664
 __do_softirq+0x244/0x9a0 kernel/softirq.c:288
 invoke_softirq kernel/softirq.c:368 [inline]
 irq_exit+0x160/0x1b0 kernel/softirq.c:409
 exiting_irq arch/x86/include/asm/apic.h:648 [inline]
 smp_apic_timer_interrupt+0x146/0x5e0 arch/x86/kernel/apic/apic.c:1102
 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x9/0x60 kernel/kcov.c:65
RSP: 0018:ffff888096eff888 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: ffff888096ef64c0 RBX: ffff8880a77c7ce0 RCX: 1ffffffff12391cf
RDX: 0000000000000000 RSI: ffff888096ef6d68 RDI: 0000000000000001
RBP: ffff888096eff8c8 R08: 0000000000005e26 R09: ffffffff88cae5b0
R10: ffff888096ef6d68 R11: ffff888096ef64c0 R12: 00000000000000bb
R13: ffffffff891c8e78 R14: ffff8880a77c7df0 R15: 0000000000000000
 __d_add fs/dcache.c:2620 [inline]
 d_add+0x4ff/0x640 fs/dcache.c:2653
 simple_lookup fs/libfs.c:68 [inline]
 simple_lookup+0xc5/0x110 fs/libfs.c:62
 lookup_slow+0x226/0x440 fs/namei.c:1695
 walk_component+0x698/0x1d00 fs/namei.c:1824
 lookup_last fs/namei.c:2292 [inline]
 path_lookupat.isra.0+0x1bb/0x7b0 fs/namei.c:2342
 filename_lookup+0x18e/0x380 fs/namei.c:2376
 user_path_at_empty+0x43/0x50 fs/namei.c:2630
 SYSC_readlinkat fs/stat.c:394 [inline]
 SyS_readlinkat fs/stat.c:382 [inline]
 SYSC_readlink fs/stat.c:421 [inline]
 SyS_readlink+0xb7/0x290 fs/stat.c:418
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f4a25411577
RSP: 002b:00007ffea2234af8 EFLAGS: 00000202 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 0000000001b64030 RCX: 00007f4a25411577
RDX: 00000000000003fc RSI: 00007ffea2234f24 RDI: 00007ffea2234b20
RBP: 00000000000003fc R08: 0000000001b640f0 R09: 00007f4a254661d0
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000001b7ccc0 R15: 0000000001b64030
Code: 00 00 00 48 b8 00 02 00 00 00 00 ad de 49 39 c4 0f 84 e2 00 00 00 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 80 3c 02 00 <75> 53 49 8b 14 24 4c 39 f2 0f 85 99 00 00 00 49 8d 7d 08 48 b8