BUG: KCSAN: data-race in copy_page_to_iter / fat16_ent_put

write to 0xffff88816367c3a6 of 2 bytes by task 29000 on cpu 0:
 fat16_ent_put+0x24/0x50 fs/fat/fatent.c:183
 fat_alloc_clusters+0x47d/0xa80 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+0x263/0x600 fs/fat/inode.c:190
 __block_write_begin_int+0x33d/0xc90 fs/buffer.c:2006
 __block_write_begin fs/buffer.c:2056 [inline]
 block_write_begin+0x73/0x170 fs/buffer.c:2117
 cont_write_begin+0x3f1/0x520 fs/buffer.c:2468
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_perform_write+0x1d4/0x3f0 mm/filemap.c:3779
 __generic_file_write_iter+0xe3/0x280 mm/filemap.c:3907
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3939
 call_write_iter include/linux/fs.h:2058 [inline]
 aio_write+0x2e0/0x3c0 fs/aio.c:1603
 io_submit_one+0x89b/0x1190 fs/aio.c:2022
 __do_sys_io_submit fs/aio.c:2081 [inline]
 __se_sys_io_submit+0x105/0x280 fs/aio.c:2051
 __x64_sys_io_submit+0x3f/0x50 fs/aio.c:2051
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

read to 0xffff88816367c000 of 1024 bytes by task 28851 on cpu 1:
 instrument_copy_to_user include/linux/instrumented.h:119 [inline]
 copyout lib/iov_iter.c:154 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:226 [inline]
 __copy_page_to_iter lib/iov_iter.c:852 [inline]
 copy_page_to_iter+0x415/0x7b0 lib/iov_iter.c:880
 copy_folio_to_iter include/linux/uio.h:153 [inline]
 filemap_read+0x117b/0x1410 mm/filemap.c:2739
 blkdev_read_iter+0x2c6/0x370 block/fops.c:594
 call_read_iter include/linux/fs.h:2052 [inline]
 new_sync_read fs/read_write.c:401 [inline]
 vfs_read+0x5a5/0x6a0 fs/read_write.c:482
 ksys_read+0xe8/0x1a0 fs/read_write.c:620
 __do_sys_read fs/read_write.c:630 [inline]
 __se_sys_read fs/read_write.c:628 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:628
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 28851 Comm: udevd Not tainted 5.19.0-rc5-syzkaller-00250-gd9919d43cbf6-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
==================================================================
I/O error, dev loop5, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
Buffer I/O error on dev loop5, logical block 0, async page read