==================================================================
BUG: KCSAN: data-race in mark_buffer_dirty_inode / sync_mapping_buffers

write to 0xffff88813d12fdc0 of 8 bytes by task 28318 on cpu 1:
 __remove_assoc_queue fs/buffer.c:481 [inline]
 fsync_buffers_list fs/buffer.c:688 [inline]
 sync_mapping_buffers+0x175/0x800 fs/buffer.c:548
 fat_file_fsync+0xa9/0x100 fs/fat/file.c:194
 vfs_fsync_range+0x107/0x120 fs/sync.c:182
 generic_write_sync include/linux/fs.h:2955 [inline]
 generic_file_write_iter+0x103/0x130 mm/filemap.c:3919
 call_write_iter include/linux/fs.h:2162 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:725
 do_iter_write+0x192/0x5c0 fs/read_write.c:851
 vfs_iter_write+0x4c/0x70 fs/read_write.c:892
 iter_file_splice_write+0x43a/0x790 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0x106/0x190 fs/splice.c:979
 do_sendfile+0x675/0xc40 fs/read_write.c:1245
 __do_sys_sendfile64 fs/read_write.c:1304 [inline]
 __se_sys_sendfile64 fs/read_write.c:1296 [inline]
 __x64_sys_sendfile64+0xb9/0x140 fs/read_write.c:1296
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813d12fdc0 of 8 bytes by task 28573 on cpu 0:
 mark_buffer_dirty_inode+0x92/0x1b0 fs/buffer.c:581
 fat16_ent_put+0x4b/0x50 fs/fat/fatent.c:183
 fat_alloc_clusters+0x493/0xab0 fs/fat/fatent.c:502
 fat_add_cluster fs/fat/inode.c:108 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x267/0x610 fs/fat/inode.c:190
 __block_write_begin_int+0x4c5/0x1010 fs/buffer.c:2010
 __block_write_begin fs/buffer.c:2060 [inline]
 block_write_begin fs/buffer.c:2120 [inline]
 cont_write_begin+0x4cf/0x7b0 fs/buffer.c:2469
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:235
 generic_perform_write+0x1c8/0x400 mm/filemap.c:3756
 __generic_file_write_iter+0xf7/0x2b0 mm/filemap.c:3883
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3915
 call_write_iter include/linux/fs.h:2162 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:725
 do_iter_write+0x192/0x5c0 fs/read_write.c:851
 vfs_writev fs/read_write.c:924 [inline]
 do_pwritev+0x235/0x440 fs/read_write.c:1021
 __do_sys_pwritev2 fs/read_write.c:1080 [inline]
 __se_sys_pwritev2 fs/read_write.c:1071 [inline]
 __x64_sys_pwritev2+0x7e/0xa0 fs/read_write.c:1071
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff88813d0addb0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28573 Comm: syz-executor.4 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================
handle_bad_sector: 163 callbacks suppressed
syz-executor.4: attempt to access beyond end of device
loop4: rw=2049, want=34, limit=16
syz-executor.4: attempt to access beyond end of device
loop4: rw=2049, want=259, limit=16
syz-executor.4: attempt to access beyond end of device
loop4: rw=2049, want=163, limit=16