[syzbot] [exfat?] WARNING in fat_add_entries

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: adc1e5c6203c Merge tag 'efi-fixes-for-v7.1-1' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14b4bb26580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7f195f6be48c12ec
dashboard link: https://syzkaller.appspot.com/bug?extid=872e83c344f0ae2cf617
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-adc1e5c6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f67d79b10054/vmlinux-adc1e5c6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f9dcdab6fabb/bzImage-adc1e5c6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+872e83...@syzkaller.appspotmail.com

loop0: detected capacity change from 128 to 0
FAT-fs (loop0): Directory bread(block 40) failed
FAT-fs (loop0): Directory bread(block 40) failed
------------[ cut here ]------------
!buffer_uptodate(bh)
WARNING: fs/buffer.c:1087 at mark_buffer_dirty+0x299/0x410 fs/buffer.c:1087, CPU#0: syz.0.0/5323
Modules linked in:
CPU: 0 UID: 0 PID: 5323 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:mark_buffer_dirty+0x299/0x410 fs/buffer.c:1087
Code: 4c 89 f7 e8 89 5d da ff 49 8b 3e be 40 00 00 00 5b 41 5c 41 5e 41 5f 5d e9 b4 63 fb ff e8 ef 93 6d ff eb 8c e8 e8 93 6d ff 90 <0f> 0b 90 e9 a5 fd ff ff e8 da 93 6d ff 90 0f 0b 90 e9 cf fd ff ff
RSP: 0018:ffffc900057df208 EFLAGS: 00010287
RAX: ffffffff82583af8 RBX: ffff888046d92000 RCX: 0000000000100000
RDX: ffffc90020802000 RSI: 00000000000029e1 RDI: 00000000000029e2
RBP: ffffc900057df401 R08: ffff888046d92007 R09: 1ffff11008db2400
R10: dffffc0000000000 R11: ffffed1008db2401 R12: dffffc0000000000
R13: 00000000000002a0 R14: dffffc0000000000 R15: ffff888046e3ba50
FS: 00007f247469b6c0(0000) GS:ffff88808c885000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f247469aff8 CR3: 0000000039246000 CR4: 0000000000352ef0
Call Trace:
<TASK>
mmb_mark_buffer_dirty+0x2f/0x200 fs/buffer.c:719
fat_add_entries+0x799/0x2320 fs/fat/dir.c:1362
vfat_add_entry+0x2def/0x3580 fs/fat/namei_vfat.c:675
vfat_create+0x148/0x270 fs/fat/namei_vfat.c:769
lookup_open fs/namei.c:4511 [inline]
open_last_lookups fs/namei.c:4611 [inline]
path_openat+0x1395/0x3860 fs/namei.c:4855
do_file_open+0x23e/0x4a0 fs/namei.c:4887
do_sys_openat2+0x113/0x200 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_creat fs/open.c:1448 [inline]
__se_sys_creat fs/open.c:1442 [inline]
__x64_sys_creat+0x8f/0xc0 fs/open.c:1442
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f247379cdd9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f247469afe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f2473a16090 RCX: 00007f247379cdd9
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000200000000e00
RBP: 00007f2473832d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2473a16128 R14: 00007f2473a16090 R15: 00007ffd5e53e4e8
</TASK>


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