loop0: detected capacity change from 0 to 8192
==================================================================
BUG: KCSAN: data-race in mark_buffer_dirty_inode / mark_buffer_dirty_inode

write to 0xffff88810625e6d8 of 8 bytes by task 3516 on cpu 0:
 mark_buffer_dirty_inode+0x18d/0x1c0 fs/buffer.c:682
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_ent_write+0xcc/0xe0 fs/fat/fatent.c:423
 fat_chain_add+0x15f/0x400 fs/fat/misc.c:136
 fat_add_cluster fs/fat/inode.c:112 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x46b/0x5e0 fs/fat/inode.c:189
 __block_write_begin_int+0x417/0xfa0 fs/buffer.c:2125
 __block_write_begin fs/buffer.c:2174 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2235
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2587
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 cont_expand_zero fs/buffer.c:2514 [inline]
 cont_write_begin+0x186/0x6b0 fs/buffer.c:2577
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 generic_cont_expand_simple+0xaa/0x150 fs/buffer.c:2478
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x2aa/0x840 fs/fat/file.c:513
 notify_change+0x814/0x8a0 fs/attr.c:495
 do_truncate fs/open.c:65 [inline]
 do_ftruncate+0x3e1/0x470 fs/open.c:181
 do_sys_ftruncate fs/open.c:199 [inline]
 __do_sys_ftruncate fs/open.c:207 [inline]
 __se_sys_ftruncate fs/open.c:205 [inline]
 __x64_sys_ftruncate+0x6a/0xc0 fs/open.c:205
 x64_sys_call+0x8e5/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:78
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810625e6d8 of 8 bytes by task 3505 on cpu 1:
 mark_buffer_dirty_inode+0x96/0x1c0 fs/buffer.c:678
 fat_mirror_bhs+0x241/0x330 fs/fat/fatent.c:398
 fat_alloc_clusters+0x994/0xa80 fs/fat/fatent.c:543
 fat_add_cluster fs/fat/inode.c:107 [inline]
 __fat_get_block fs/fat/inode.c:154 [inline]
 fat_get_block+0x25c/0x5e0 fs/fat/inode.c:189
 __block_write_begin_int+0x417/0xfa0 fs/buffer.c:2125
 __block_write_begin fs/buffer.c:2174 [inline]
 block_write_begin+0x7b/0x170 fs/buffer.c:2235
 cont_write_begin+0x486/0x6b0 fs/buffer.c:2587
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:229
 generic_perform_write+0x1b4/0x580 mm/filemap.c:4019
 __generic_file_write_iter+0xa1/0x120 mm/filemap.c:4121
 generic_file_write_iter+0x7d/0x1d0 mm/filemap.c:4147
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x78f/0x900 fs/read_write.c:590
 ksys_write+0xeb/0x1b0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:652
 x64_sys_call+0x27dd/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff8881060fd708

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3505 Comm: syz.0.25 Not tainted 6.11.0-rc4-syzkaller-00011-g521b1e7f4cf0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================
syz.0.25 (3505) used greatest stack depth: 10856 bytes left