syzbot

INFO: task restorecond:1995 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
restorecond     D ffff8801d62bfac8 28640  1995      1 0x00000000
 ffff8801d62bfac8 ffff8801d671c740 4298df700dd4ba50 ffff8801d671c740
 0000000000000001 ffff8801d671d000 ffff8801db61f180 ffff8801db61f1a8
 ffff8801db61e898 ffffffff82e151c0 ffff8801d671c740 ffffed003ac57001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff8150d753>] vfs_setxattr+0x93/0xf0 fs/xattr.c:132
 [<ffffffff8150d974>] setxattr+0x1c4/0x390 fs/xattr.c:358
 [<ffffffff8150dc95>] path_setxattr+0x155/0x170 fs/xattr.c:379
 [<ffffffff8150e148>] SYSC_lsetxattr fs/xattr.c:401 [inline]
 [<ffffffff8150e148>] SyS_lsetxattr+0x38/0x50 fs/xattr.c:397
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
2 locks held by restorecond/1995:
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff814fcd3f>] sb_start_write include/linux/fs.h:1517 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff814fcd3f>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff8150d753>] vfs_setxattr+0x93/0xf0 fs/xattr.c:132
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 2179 Comm: syz-executor711 Not tainted 4.4.174+ #4
task: ffff8800b4d10000 task.stack: ffff8800b2248000
RIP: 0010:[<ffffffff813095f1>]  [<ffffffff813095f1>] __sanitizer_cov_trace_pc+0x1/0x50 kernel/kcov.c:93
RSP: 0018:ffff8800b224fba0  EFLAGS: 00000282
RAX: 0000000000000001 RBX: ffffffff82fb8bc0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff81745460 RDI: ffff8800b4d108c4
RBP: ffff8800b224fbb0 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffff8801d6b4a16c R14: ffff8800b224fe44 R15: 0000000000000000
FS:  00000000017d1880(0063) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001d92308 CR3: 00000000b57b4000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b224fbb0 ffffffff81b0adb9 ffff8800b224fbd0 ffffffff8123d925
 ffff8800b224fe44 ffffffff82fb8bc0 ffff8800b224fbe8 ffffffff8123a90e
 0000000000000000 ffff8800b224fc40 ffffffff81745465 ffff8801d6bb5db0
Call Trace:
 [<ffffffff8123d925>] __rcu_is_watching kernel/rcu/tree.c:999 [inline]
 [<ffffffff8123d925>] rcu_is_watching+0x15/0xb0 kernel/rcu/tree.c:1013
 [<ffffffff8123a90e>] rcu_read_lock_sched_held+0x8e/0x130 kernel/rcu/update.c:103
 [<ffffffff81745465>] trace_ext4_es_lookup_extent_exit include/trace/events/ext4.h:2384 [inline]
 [<ffffffff81745465>] ext4_es_lookup_extent+0x985/0xc30 fs/ext4/extents_status.c:835
 [<ffffffff8164b026>] ext4_map_blocks+0x156/0x16f0 fs/ext4/inode.c:492
 [<ffffffff81634dcb>] ext4_seek_data fs/ext4/file.c:576 [inline]
 [<ffffffff81634dcb>] ext4_llseek+0x68b/0x970 fs/ext4/file.c:717
 [<ffffffff81497af3>] vfs_llseek fs/read_write.c:260 [inline]
 [<ffffffff81497af3>] SYSC_lseek fs/read_write.c:285 [inline]
 [<ffffffff81497af3>] SyS_lseek+0x113/0x180 fs/read_write.c:276
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: e8 f5 b8 17 00 48 8b 55 c8 e9 d2 fe ff ff 48 89 df e8 e4 b8 17 00 e9 ac fe ff ff 4c 89 f7 e8 d7 b8 17 00 e9 42 fe ff ff 66 90 55 <48> 89 e5 48 8b 75 08 65 48 8b 04 25 80 67 01 00 65 8b 15 08 d1 
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6c2f80 task.stack: ffff8800001e8000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001efc88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001efcb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001d94000 CR3: 00000001d425c000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8800001efcd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001efd30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1