syzbot

loop0: detected capacity change from 0 to 8192
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kernel BUG at fs/buffer.c:579!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4540 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : mark_buffer_dirty_inode+0x288/0x28c fs/buffer.c:579
lr : mark_buffer_dirty_inode+0x288/0x28c fs/buffer.c:579
sp : ffff800020fd71a0
x29: ffff800020fd71b0 x28: ffff800011cda820 x27: 0000000000000000
x26: ffff0000e52f8368 x25: dfff800000000000 x24: 0000000000000000
x23: ffff800020fd7300 x22: dfff800000000000 x21: 1fffe0001ca5f0b1
x20: ffff0000e52f8588 x19: ffff0000e52d52b8 x18: ffff800011b9bf60
x17: 1fffe00033ea637e x16: ffff8000082d92bc x15: 0000000000000000
x14: 0000000000000001 x13: 1fffff80007a6240 x12: 0000000000ff0100
x11: ff00800008a8f4e4 x10: 0000000000000000 x9 : ffff800008a8f4e4
x8 : ffff0000d576d340 x7 : ffff800008937890 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : ffff800008a8f738
x2 : 0000000000000001 x1 : ffff800011b9ebc0 x0 : 0000000000000000
Call trace:
 mark_buffer_dirty_inode+0x288/0x28c fs/buffer.c:579
 fat16_ent_put+0xa0/0xc0 fs/fat/fatent.c:184
 fat_alloc_clusters+0x46c/0xb64 fs/fat/fatent.c:503
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x33c/0x930 fs/fat/inode.c:190
 __block_write_begin_int+0x350/0x1388 fs/buffer.c:1991
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin fs/buffer.c:2102 [inline]
 cont_write_begin+0x53c/0x780 fs/buffer.c:2456
 fat_write_begin+0x98/0x150 fs/fat/inode.c:235
 generic_perform_write+0x234/0x4f4 mm/filemap.c:3862
 __generic_file_write_iter+0x130/0x250 mm/filemap.c:3960
 generic_file_write_iter+0xb4/0x2b0 mm/filemap.c:3989
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3ec/0x7f0 fs/read_write.c:584
 ksys_pwrite64 fs/read_write.c:699 [inline]
 __do_sys_pwrite64 fs/read_write.c:709 [inline]
 __se_sys_pwrite64 fs/read_write.c:706 [inline]
 __arm64_sys_pwrite64+0x174/0x20c fs/read_write.c:706
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: 9101c3ff d50323bf d65f03c0 97e8704e (d4210000) 
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