WARNING in verify_dirent_name

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    43b815c6 Merge tag 'armsoc-fixes' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12165d0b600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1ec3be9936e004f6
dashboard link: https://syzkaller.appspot.com/bug?extid=76e3977ad1b8cc4d113a
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+76e3977ad1b8cc4d113a@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
WARNING: CPU: 1 PID: 25558 at fs/readdir.c:150 verify_dirent_name+0x67/0x80  
fs/readdir.c:150
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 25558 Comm: syz-executor.2 Not tainted 5.4.0-rc1+ #0
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
 panic+0x2dc/0x755 kernel/panic.c:220
 __warn.cold+0x2f/0x3c kernel/panic.c:581
 report_bug+0x289/0x300 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:verify_dirent_name+0x67/0x80 fs/readdir.c:150
Code: 19 b6 ff 44 89 e0 5b 41 5c 5d c3 e8 43 19 b6 ff 0f 0b e8 3c 19 b6 ff  
41 bc fb ff ff ff 5b 44 89 e0 41 5c 5d c3 e8 29 19 b6 ff <0f> 0b 41 bc fb  
ff ff ff eb ca 0f 1f 44 00 00 66 2e 0f 1f 84 00 00
RSP: 0018:ffff88808db87ad0 EFLAGS: 00010212
RAX: 0000000000040000 RBX: 000000000000000c RCX: ffffc900143e7000
RDX: 0000000000004d26 RSI: ffffffff81bcf9b7 RDI: ffff88808db87cd3
RBP: ffff88808db87ae0 R08: ffff88808f5c41c0 R09: 0000000000000004
R10: fffffbfff120d9b8 R11: ffffffff8906cdc3 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000004 R15: ffff88808db87e50
 filldir64+0x40/0x670 fs/readdir.c:356
 dir_emit include/linux/fs.h:3542 [inline]
 __fat_readdir+0xd9e/0x1cb0 fs/fat/dir.c:677
 fat_readdir+0x44/0x60 fs/fat/dir.c:704
 iterate_dir+0x47f/0x5e0 fs/readdir.c:105
 ksys_getdents64+0x1ce/0x320 fs/readdir.c:412
 __do_sys_getdents64 fs/readdir.c:431 [inline]
 __se_sys_getdents64 fs/readdir.c:428 [inline]
 __x64_sys_getdents64+0x73/0xb0 fs/readdir.c:428
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc825c13c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
RDX: 0000000000001000 RSI: 00000000200005c0 RDI: 0000000000000007
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc825c146d4
R13: 00000000004c0533 R14: 00000000004d2c58 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


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