------------[ cut here ]------------
WARNING: CPU: 0 PID: 4436 at fs/buffer.c:1081 mark_buffer_dirty+0x383/0x7a0 fs/buffer.c:1081
Modules linked in:
CPU: 0 PID: 4436 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:mark_buffer_dirty+0x383/0x7a0 fs/buffer.c:1081
Code: 13 6b e2 ff 49 8b 3f be 04 00 00 00 5b 41 5c 41 5d 41 5e 41 5f 5d e9 ac a8 fc ff e8 37 26 91 ff e9 43 ff ff ff e8 2d 26 91 ff <0f> 0b e9 ba fc ff ff e8 21 26 91 ff 0f 0b e9 00 fd ff ff e8 15 26
RSP: 0018:ffffc900033b73d8 EFLAGS: 00010293
RAX: ffffffff81f10cb3 RBX: ffff88806ef242b8 RCX: ffff88807a18bc00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffff888148c83f01 R08: ffff88806ef242bf R09: 1ffff1100dde4857
R10: dffffc0000000000 R11: ffffed100dde4858 R12: dffffc0000000000
R13: ffff888056250368 R14: ffffea0001a5b198 R15: ffff88806ef242b8
FS:  00007f1c335106c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1c325eb840 CR3: 0000000023af9000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 mark_buffer_dirty_inode+0x82/0x2c0 fs/buffer.c:575
 fat12_ent_put+0x1af/0x2e0 fs/fat/fatent.c:173
 fat_ent_write+0xae/0x180 fs/fat/fatent.c:417
 fat_chain_add+0x3e5/0x880 fs/fat/misc.c:140
 fat_add_cluster fs/fat/inode.c:113 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x761/0xae0 fs/fat/inode.c:190
 __block_write_begin_int+0x577/0x1ab0 fs/buffer.c:1991
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x96/0x1e0 fs/buffer.c:2102
 cont_write_begin+0x5f9/0x800 fs/buffer.c:2456
 fat_write_begin+0x93/0x160 fs/fat/inode.c:235
 generic_perform_write+0x2fa/0x5c0 mm/filemap.c:3862
 __generic_file_write_iter+0x148/0x2a0 mm/filemap.c:3960
 generic_file_write_iter+0xab/0x2e0 mm/filemap.c:3989
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x482/0x9a0 fs/read_write.c:584
 ksys_write+0x14d/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1c3259e159
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:00007f1c33510028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1c32825fa0 RCX: 00007f1c3259e159
RDX: 00000000fffffceb RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007f1c3263506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1c32826038 R14: 00007f1c32825fa0 R15: 00007fff715da428
 </TASK>