FAT-fs (loop2): invalid media value (0x21)
FAT-fs (loop2): Can't find a valid FAT filesystem
INFO: task syz-executor1:11871 blocked for more than 140 seconds.
      Not tainted 4.9.124-g09eb2ba #31
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor1   D27864 11871      1 0x00000004
 ffff8801cda2b000 0000000000000000 ffff8801b686ea00 ffffffff84629800
 ffff8801db221c18 ffff88019aa0f4e0 ffffffff839f0afd ffffffff81237da7
 0000000000000000 ffff8801cda2b8c0 0000000600000007 ffff8801db2224e8
Call Trace:
 [<ffffffff839f20ff>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff839fc524>] rwsem_down_read_failed+0x1e4/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81eed8d8>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff839fb452>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff839fb452>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff81599441>] inode_lock_shared include/linux/fs.h:776 [inline]
 [<ffffffff81599441>] lookup_slow+0x141/0x470 fs/namei.c:1645
 [<ffffffff815a5ac6>] walk_component+0x716/0x1bb0 fs/namei.c:1784
 [<ffffffff815a77e9>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a885d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff815729bd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff815729bd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813689dc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.?..}, at: [<ffffffff81428248>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3771:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839ffba2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82125402>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor1/11871:
 #0:  (&sb->s_type->i_mutex_key#21){++++++}, at: [<ffffffff81599441>] inode_lock_shared include/linux/fs.h:776 [inline]
 #0:  (&sb->s_type->i_mutex_key#21){++++++}, at: [<ffffffff81599441>] lookup_slow+0x141/0x470 fs/namei.c:1645
2 locks held by syz-executor1/32522:
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e50cf>] sb_start_write include/linux/fs.h:1573 [inline]
 #0:  (sb_writers#15){.+.+.+}, at: [<ffffffff815e50cf>] mnt_want_write+0x3f/0xb0 fs/namespace.c:391
 #1:  (&sb->s_type->i_mutex_key#21){++++++}, at: [<ffffffff815a9585>] inode_lock include/linux/fs.h:766 [inline]
 #1:  (&sb->s_type->i_mutex_key#21){++++++}, at: [<ffffffff815a9585>] do_last fs/namei.c:3312 [inline]
 #1:  (&sb->s_type->i_mutex_key#21){++++++}, at: [<ffffffff815a9585>] path_openat+0xed5/0x3590 fs/namei.c:3534

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d863fd08 ffffffff81eb95e9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9fa0 ffff8801d863fd40
 ffffffff81ec4927 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ec4927>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ec48ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810ba0a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81368f74>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81368f74>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368f74>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368f74>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119f3cd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a01b9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 32499 Comm: syz-executor1 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff880189366000 task.stack: ffff88019e558000
RIP: 0010:[<ffffffff81628aa8>] 
c [<ffffffff81628aa8>] __find_get_block+0x8/0x4c0 fs/buffer.c:1355
RSP: 0018:ffff88019e55f298  EFLAGS: 00000246
RAX: 0000000000040000 RBX: 0000000000000001 RCX: ffffc900036ed000
RDX: 0000000000000200 RSI: 0000000000000041 RDI: ffff8801d5dc05c0
RBP: ffff88019e55f2a8 R08: ffff880189366960 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003126cd27 R12: ffffea0006ff175c
R13: ffffea0006ff1740 R14: 0000000000000200 R15: dffffc0000000000
FS:  00007f1ce1da0700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1a68cac000 CR3: 00000001ba623000 CR4: 00000000001606f0
Stack:
 0000000000000200
c dffffc0000000000
c ffff88019e55f348
c ffffffff81629ae9
c
 ffff88019e55f328
c ffff8801d5dc05c8
c 0000000000000000
c ffffed003abb80b9
c
 ffff880189366000
c ffff8801d5dc0780
c ffffea0006ff1760
c 0000000000000008
c
Call Trace:
 [<ffffffff81629ae9>] __getblk_slow fs/buffer.c:1101 [inline]
 [<ffffffff81629ae9>] __getblk_gfp+0x189/0x710 fs/buffer.c:1386
 [<ffffffff8162d48d>] __bread_gfp+0x2d/0x270 fs/buffer.c:1420
 [<ffffffff818bc678>] sb_bread include/linux/buffer_head.h:300 [inline]
 [<ffffffff818bc678>] fat__get_entry+0x4c8/0x8f0 fs/fat/dir.c:100
 [<ffffffff818c4477>] fat_get_entry fs/fat/dir.c:128 [inline]
 [<ffffffff818c4477>] fat_search_long+0x277/0x1180 fs/fat/dir.c:477
 [<ffffffff818de9e4>] vfat_find+0x134/0x180 fs/fat/namei_vfat.c:708
 [<ffffffff818df1c1>] vfat_lookup+0xe1/0x530 fs/fat/namei_vfat.c:731
 [<ffffffff8159f93d>] lookup_open+0x63d/0x1930 fs/namei.c:3203
 [<ffffffff815a95a8>] do_last fs/namei.c:3315 [inline]
 [<ffffffff815a95a8>] path_openat+0xef8/0x3590 fs/namei.c:3534
 [<ffffffff815aff07>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff815726dd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff81572a00>] SYSC_openat fs/open.c:1099 [inline]
 [<ffffffff81572a00>] SyS_openat+0x30/0x40 fs/open.c:1093
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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