INFO: rcu detected stall in rw_verify_area

Sat Jan 19 12:53:23 UTC 2019

On Sat, Jan 19, 2019 at 1:39 PM syzbot
<syzbot+3d95205bfac60602a727 at syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    9673b4aa71ca Add linux-next specific files for 20190118
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10c2097f400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4086e03c3128165
> dashboard link: https://syzkaller.appspot.com/bug?extid=3d95205bfac60602a727
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14a02f6f400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16c4dc28c00000

+Ingo, Peter

Looks like another problem with scheduler as the repro uses
perf_event_open and sched_setattr.

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+3d95205bfac60602a727 at syzkaller.appspotmail.com
>
> hrtimer: interrupt took 39380 ns
> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
> rcu:    (detected by 0, t=10502 jiffies, g=5593, q=4)
> rcu: All QSes seen, last rcu_preempt kthread activity 10503
> (4295058157-4295047654), jiffies_till_next_fqs=1, root ->qsmask 0x0
> syz-executor570 R  running task    23848  7948   7931 0x00000000
> Call Trace:
>   <IRQ>
>   sched_show_task kernel/sched/core.c:5296 [inline]
>   sched_show_task.cold+0x271/0x2d3 kernel/sched/core.c:5271
>   print_other_cpu_stall.cold+0x7f2/0x8bb kernel/rcu/tree.c:1324
>   check_cpu_stall kernel/rcu/tree.c:1452 [inline]
>   rcu_pending kernel/rcu/tree.c:3114 [inline]
>   rcu_sched_clock_irq+0xf36/0x1380 kernel/rcu/tree.c:2555
>   update_process_times+0x32/0x80 kernel/time/timer.c:1635
>   tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:161
>   tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1271
>   __run_hrtimer kernel/time/hrtimer.c:1389 [inline]
>   __hrtimer_run_queues+0x3a7/0x1050 kernel/time/hrtimer.c:1451
>   hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509
>   local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
>   smp_apic_timer_interrupt+0x18d/0x760 arch/x86/kernel/apic/apic.c:1060
>   apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
>   </IRQ>
> RIP: 0010:__sanitizer_cov_trace_pc+0x26/0x50 kernel/kcov.c:101
> Code: 46 df ff ff 55 48 89 e5 48 8b 75 08 65 48 8b 04 25 40 ee 01 00 65 8b
> 15 a8 b4 7f 7e 81 e2 00 01 1f 00 75 2b 8b 90 e0 12 00 00 <83> fa 02 75 20
> 48 8b 88 e8 12 00 00 8b 80 e4 12 00 00 48 8b 11 48
> RSP: 0018:ffff88808d0bf460 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> RAX: ffff888092ba00c0 RBX: ffff888097e1bc80 RCX: ffffffff835a5f5c
> RDX: 0000000000000000 RSI: ffffffff835a5bf6 RDI: 0000000000000005
> RBP: ffff88808d0bf460 R08: ffff888092ba00c0 R09: ffffed1015cc5b90
> R10: ffffed1015cc5b8f R11: ffff8880ae62dc7b R12: ffff88821bc94bb0
> R13: ffff88821bc94bb0 R14: ffff8880a3586958 R15: ffff88808d0bf5f0
>   aa_file_perm+0x226/0x1180 security/apparmor/file.c:615
>   common_file_perm+0x1cb/0x820 security/apparmor/lsm.c:459
>   apparmor_file_permission+0x25/0x30 security/apparmor/lsm.c:472
>   security_file_permission+0x7e/0x320 security/security.c:1326
>   rw_verify_area+0x110/0x360 fs/read_write.c:391
>   do_iter_write+0x100/0x610 fs/read_write.c:951
>   vfs_iter_write+0x77/0xb0 fs/read_write.c:969
>   iter_file_splice_write+0x885/0xfc0 fs/splice.c:749
>   do_splice_from fs/splice.c:851 [inline]
>   direct_splice_actor+0x126/0x1a0 fs/splice.c:1023
>   splice_direct_to_actor+0x3be/0x9d0 fs/splice.c:978
>   do_splice_direct+0x2c7/0x420 fs/splice.c:1066
>   do_sendfile+0x61a/0xe60 fs/read_write.c:1436
>   __do_sys_sendfile64 fs/read_write.c:1491 [inline]
>   __se_sys_sendfile64 fs/read_write.c:1483 [inline]
>   __x64_sys_sendfile64+0x15a/0x240 fs/read_write.c:1483
>   do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x446a19
> Code: e8 dc e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 4b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fc79f06bda8 EFLAGS: 00000297 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 00000000006dcc38 RCX: 0000000000446a19
> RDX: 0000000020000380 RSI: 0000000000000003 RDI: 0000000000000003
> RBP: 00000000006dcc30 R08: 0000000000000000 R09: 0000000000000000
> R10: 00008080fffffffe R11: 0000000000000297 R12: 00000000006dcc3c
> R13: 00008080fffffffe R14: 00007fc79f06c9c0 R15: 00000000006dcd2c
> rcu: rcu_preempt kthread starved for 10583 jiffies! g5593 f0x2
> RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
> rcu: RCU grace-period kthread stack dump:
> rcu_preempt     R  running task    25832    10      2 0x80000000
> Call Trace:
>   context_switch kernel/sched/core.c:2834 [inline]
>   __schedule+0x897/0x1e60 kernel/sched/core.c:3475
>   schedule+0xfe/0x350 kernel/sched/core.c:3519
>   schedule_timeout+0x14a/0x250 kernel/time/timer.c:1803
>   rcu_gp_fqs_loop+0x6d4/0x980 kernel/rcu/tree.c:1982
>   rcu_gp_kthread+0x2bb/0xc10 kernel/rcu/tree.c:2139
>   kthread+0x357/0x430 kernel/kthread.c:247
>   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
> sched: RT throttling activated
>
>
> ---
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