WARNING in filldir64

[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=10721dfb600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=fb0b431ccdf08c1c
dashboard link: https://syzkaller.appspot.com/bug?extid=3031f712c7ad5dd4d926
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

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+3031f712c7ad5dd4d926@xxxxxxxxxxxxxxxxxxxxxxxxx

------------[ cut here ]------------
WARNING: CPU: 1 PID: 10405 at fs/readdir.c:150 verify_dirent_name  
fs/readdir.c:150 [inline]
WARNING: CPU: 1 PID: 10405 at fs/readdir.c:150 filldir64+0x524/0x620  
fs/readdir.c:356
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 10405 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+0x1d8/0x2f8 lib/dump_stack.c:113
 panic+0x25c/0x799 kernel/panic.c:220
 __warn+0x20e/0x210 kernel/panic.c:581
 report_bug+0x1b6/0x2f0 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 do_error_trap+0xd7/0x440 arch/x86/kernel/traps.c:272
 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:291
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:verify_dirent_name fs/readdir.c:150 [inline]
RIP: 0010:filldir64+0x524/0x620 fs/readdir.c:356
Code: 00 00 c7 03 f2 ff ff ff b8 f2 ff ff ff 48 83 c4 60 5b 41 5c 41 5d 41  
5e 41 5f 5d c3 e8 55 2c b9 ff 0f 0b eb 07 e8 4c 2c b9 ff <0f> 0b 49 83 c6  
24 4c 89 f0 48 c1 e8 03 42 8a 04 20 84 c0 0f 85 b6
RSP: 0018:ffff8880a3dc7b88 EFLAGS: 00010283
RAX: ffffffff81ba0624 RBX: 000000000000000c RCX: 0000000000040000
RDX: ffffc9000a588000 RSI: 00000000000021f1 RDI: 00000000000021f2
RBP: ffff8880a3dc7c10 R08: ffffffff81ba0134 R09: 0000000000000004
R10: fffffbfff1120afb R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880a3dc7d30 R14: ffff8880a3dc7e88 R15: 000000000000000c
 dir_emit include/linux/fs.h:3542 [inline]
 __fat_readdir+0x1320/0x1a50 fs/fat/dir.c:677
 fat_readdir+0x46/0x50 fs/fat/dir.c:704
 iterate_dir+0x2a4/0x520 fs/readdir.c:107
 ksys_getdents64+0x1ea/0x3f0 fs/readdir.c:412
 __do_sys_getdents64 fs/readdir.c:431 [inline]
 __se_sys_getdents64 fs/readdir.c:428 [inline]
 __x64_sys_getdents64+0x7a/0x90 fs/readdir.c:428
 do_syscall_64+0xf7/0x1c0 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:00007f943ff4bc78 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
RDX: 0000000000001000 RSI: 00000000200005c0 RDI: 0000000000000005
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f943ff4c6d4
R13: 00000000004c0533 R14: 00000000004d2c58 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


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