------------[ cut here ]------------
WARNING: CPU: 1 PID: 11915 at fs/buffer.c:1177 mark_buffer_dirty+0x2e5/0x520 fs/buffer.c:1177
Modules linked in:
CPU: 1 UID: 0 PID: 11915 Comm: syz.7.126 Not tainted 6.12.0-rc7-syzkaller-00125-gcfaaa7d010d1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
RIP: 0010:mark_buffer_dirty+0x2e5/0x520 fs/buffer.c:1177
Code: 89 df e8 ee 7a db ff 48 8b 3b be 20 00 00 00 5b 41 5e 41 5f 5d e9 fb e8 fb ff e8 66 c1 74 ff e9 73 ff ff ff e8 5c c1 74 ff 90 <0f> 0b 90 e9 61 fd ff ff e8 4e c1 74 ff 90 0f 0b 90 e9 88 fd ff ff
RSP: 0018:ffffc900046f73b0 EFLAGS: 00010293
RAX: ffffffff82202854 RBX: ffff88804f62d001 RCX: ffff88802fff9e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff822025b1 R09: 1ffff11009ec5a00
R10: dffffc0000000000 R11: ffffed1009ec5a01 R12: dffffc0000000000
R13: ffff88804f62d000 R14: ffff88804f62d000 R15: ffff8880235f9f78
FS:  00007f22e05876c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055b90b16b000 CR3: 00000000223a4000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 mark_buffer_dirty_inode+0x89/0x300 fs/buffer.c:672
 fat12_ent_put+0x1af/0x2e0 fs/fat/fatent.c:173
 fat_free_clusters+0x4c7/0xf60 fs/fat/fatent.c:597
 fat_add_cluster fs/fat/inode.c:114 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x8ff/0xd00 fs/fat/inode.c:189
 __block_write_begin_int+0x50c/0x1a70 fs/buffer.c:2121
 block_write_begin fs/buffer.c:2231 [inline]
 cont_write_begin+0x6e2/0x9d0 fs/buffer.c:2582
 fat_write_begin+0x76/0x140 fs/fat/inode.c:228
 cont_expand_zero fs/buffer.c:2509 [inline]
 cont_write_begin+0x338/0x9d0 fs/buffer.c:2572
 fat_write_begin+0x76/0x140 fs/fat/inode.c:228
 generic_cont_expand_simple+0x18f/0x2b0 fs/buffer.c:2473
 fat_cont_expand+0x60/0x1e0 fs/fat/file.c:223
 fat_fallocate+0x23a/0x2f0 fs/fat/file.c:301
 vfs_fallocate+0x569/0x6e0 fs/open.c:333
 ksys_fallocate fs/open.c:356 [inline]
 __do_sys_fallocate fs/open.c:364 [inline]
 __se_sys_fallocate fs/open.c:362 [inline]
 __x64_sys_fallocate+0xbd/0x110 fs/open.c:362
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f22df77e719
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f22e0587038 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f22df935f80 RCX: 00007f22df77e719
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f22df7f175e R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000c8ab R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f22df935f80 R15: 00007ffdac98cf98
 </TASK>