syzbot

FAT-fs (loop0): Can't find a valid FAT filesystem
__loop_clr_fd: partition scan of loop5 failed (rc=-22)
FAT-fs (loop0): bogus number of reserved sectors
FAT-fs (loop0): Can't find a valid FAT filesystem
__loop_clr_fd: partition scan of loop5 failed (rc=-22)
INFO: task syz-executor.1:387 blocked for more than 140 seconds.
      Not tainted 5.0.0-rc8+ #88
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D24448   387      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2844 [inline]
 __schedule+0x817/0x1cc0 kernel/sched/core.c:3485
 schedule+0x92/0x180 kernel/sched/core.c:3529
 d_wait_lookup fs/dcache.c:2436 [inline]
 d_alloc_parallel+0x11cc/0x1bc0 fs/dcache.c:2518
 __lookup_slow+0x1ab/0x500 fs/namei.c:1654
 lookup_slow+0x58/0x80 fs/namei.c:1688
 mountpoint_last fs/namei.c:2665 [inline]
 path_mountpoint+0x5d2/0x1e60 fs/namei.c:2695
 filename_mountpoint+0x18e/0x390 fs/namei.c:2717
 user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2747
 ksys_umount+0x164/0xe70 fs/namespace.c:1643
 __do_sys_umount fs/namespace.c:1669 [inline]
 __se_sys_umount fs/namespace.c:1667 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1667
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a877
Code: Bad RIP value.
RSP: 002b:00007ffcb294b728 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045a877
RDX: 0000000000402e60 RSI: 0000000000000002 RDI: 00007ffcb294b7d0
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000009
R10: 0000000000000005 R11: 0000000000000206 R12: 00007ffcb294c860
R13: 0000000001f01940 R14: 0000000000000000 R15: 0000000000000001

Showing all locks held in the system:
1 lock held by khungtaskd/1039:
 #0: 00000000df2774a1 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4389
1 lock held by rsyslogd/7854:
 #0: 0000000038fafabc (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:795
2 locks held by getty/7999:
 #0: 0000000006e22aea (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000be2230e4 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8000:
 #0: 000000008ce50ded (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000ee8bd052 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8001:
 #0: 000000004852b087 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 000000008fc32e81 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8002:
 #0: 00000000189c9ca1 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000bafdf98c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8003:
 #0: 00000000ef192388 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000748dc1c0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8004:
 #0: 00000000290520d9 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000e3cfc20c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
2 locks held by getty/8005:
 #0: 0000000058d7c72b (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341
 #1: 00000000de5dec3c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x232/0x1b70 drivers/tty/n_tty.c:2154
1 lock held by syz-executor.1/387:
 #0: 00000000b2c90fca (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:767 [inline]
 #0: 00000000b2c90fca (&type->i_mutex_dir_key#8){++++}, at: lookup_slow+0x4a/0x80 fs/namei.c:1687
3 locks held by syz-executor.1/395:
 #0: 00000000017f38ad (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds fs/exec.c:1407 [inline]
 #0: 00000000017f38ad (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 fs/exec.c:1750
 #1: 00000000b2c90fca (&type->i_mutex_dir_key#8){++++}, at: inode_lock_shared include/linux/fs.h:767 [inline]
 #1: 00000000b2c90fca (&type->i_mutex_dir_key#8){++++}, at: do_last fs/namei.c:3323 [inline]
 #1: 00000000b2c90fca (&type->i_mutex_dir_key#8){++++}, at: path_openat+0x1e79/0x4690 fs/namei.c:3534
 #2: 00000000a7e3bf87 (&fi->mutex){+.+.}, at: fuse_lock_inode+0xba/0xf0 fs/fuse/inode.c:364

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 1039 Comm: khungtaskd Not tainted 5.0.0-rc8+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1be/0x236 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
 watchdog+0x9df/0xee0 kernel/hung_task.c:287
 kthread+0x357/0x430 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3868 Comm: udevd Not tainted 5.0.0-rc8+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__lock_acquire+0x29f/0x4700 kernel/locking/lockdep.c:3280
Code: 00 41 0f b7 42 20 49 8d 7a 08 48 89 fa 48 c1 ea 03 66 25 00 e0 09 f0 66 41 89 42 20 48 b8 00 00 00 00 00 fc ff df 80 3c 02 00 <0f> 85 54 2d 00 00 48 8b 45 18 49 8d 7a 10 48 89 fa 48 c1 ea 03 49
RSP: 0018:ffff888095bdf950 EFLAGS: 00000046
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 1ffff11012b7a971 RSI: 0000000000000039 RDI: ffff888095bd4b88
RBP: ffff888095bdfb18 R08: 0000000000000000 R09: 0000000000000001
R10: ffff888095bd4b80 R11: 0000000000000001 R12: ffffffff889b2708
R13: 0000000000000001 R14: 0000000000000039 R15: ffff888095bd4300
FS:  00007f6886cd57a0(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 0000000095afe000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
 seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline]
 read_seqcount_begin include/linux/seqlock.h:164 [inline]
 ktime_get_ts64+0xe2/0x3f0 kernel/time/timekeeping.c:883
 select_estimate_accuracy+0xd4/0x330 fs/select.c:87
 ep_poll+0x3b3/0xe50 fs/eventpoll.c:1761
 do_epoll_wait+0x1b3/0x200 fs/eventpoll.c:2216
 __do_sys_epoll_wait fs/eventpoll.c:2226 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2223 [inline]
 __x64_sys_epoll_wait+0x97/0xf0 fs/eventpoll.c:2223
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f68863e9943
Code: 00 31 d2 48 29 c2 64 89 11 48 83 c8 ff eb ea 90 90 90 90 90 90 90 90 83 3d b5 dc 2a 00 00 75 13 49 89 ca b8 e8 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 3b c4 00 00 48 89 04 24
RSP: 002b:00007ffddfe20798 EFLAGS: 00000246 ORIG_RAX: 00000000000000e8
RAX: ffffffffffffffda RBX: 0000000000000bb8 RCX: 00007f68863e9943
RDX: 0000000000000008 RSI: 00007ffddfe20890 RDI: 000000000000000a
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000bb8 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000000000000 R14: 0000000001461f60 R15: 0000000001412030