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BUG: KCSAN: data-race in _copy_to_iter / fat16_ent_put

write to 0xffff8881145fb346 of 2 bytes by task 28741 on cpu 0:
 fat16_ent_put+0x28/0x60 fs/fat/fatent.c:183
 fat_alloc_clusters+0x4b5/0xa60 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+0x25c/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x2ed/0xc40 fs/buffer.c:1991
 __block_write_begin fs/buffer.c:2041 [inline]
 block_write_begin+0x7c/0x180 fs/buffer.c:2102
 cont_write_begin+0x3d1/0x500 fs/buffer.c:2456
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1c3/0x3d0 mm/filemap.c:3773
 __generic_file_write_iter+0xe6/0x290 mm/filemap.c:3901
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:3933
 do_iter_write+0x418/0x700 fs/read_write.c:861
 vfs_iter_write+0x50/0x70 fs/read_write.c:902
 iter_file_splice_write+0x42b/0x7b0 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:931
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:886
 do_splice_direct+0x104/0x180 fs/splice.c:974
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff8881145fb000 of 1377 bytes by task 27770 on cpu 1:
 instrument_copy_to_user include/linux/instrumented.h:120 [inline]
 copyout lib/iov_iter.c:169 [inline]
 _copy_to_iter+0x136/0x8f0 lib/iov_iter.c:529
 copy_page_to_iter+0x1ba/0x3c0 lib/iov_iter.c:727
 copy_folio_to_iter include/linux/uio.h:172 [inline]
 filemap_read+0x11ae/0x14b0 mm/filemap.c:2746
 blkdev_read_iter+0x2ca/0x370 block/fops.c:591
 call_read_iter include/linux/fs.h:2183 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x39a/0x560 fs/read_write.c:470
 ksys_read+0xeb/0x1a0 fs/read_write.c:613
 __do_sys_read fs/read_write.c:623 [inline]
 __se_sys_read fs/read_write.c:621 [inline]
 __x64_sys_read+0x42/0x50 fs/read_write.c:621
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27770 Comm: udevd Not tainted 6.2.0-rc8-syzkaller-00151-g925cf0457d7e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
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