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BUG: KCSAN: data-race in _copy_to_iter / fat16_ent_put

write to 0xffff88811cde7396 of 2 bytes by task 21473 on cpu 1:
 fat16_ent_put+0x28/0x60 fs/fat/fatent.c:183
 fat_ent_write+0x62/0xe0 fs/fat/fatent.c:417
 fat_chain_add+0x15f/0x400 fs/fat/misc.c:136
 fat_add_cluster fs/fat/inode.c:113 [inline]
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x467/0x5e0 fs/fat/inode.c:190
 __block_write_begin_int+0x3c0/0xf30 fs/buffer.c:2128
 __block_write_begin fs/buffer.c:2178 [inline]
 block_write_begin+0x7c/0x180 fs/buffer.c:2239
 cont_write_begin+0x4c0/0x6f0 fs/buffer.c:2597
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_perform_write+0x1cf/0x410 mm/filemap.c:3923
 __generic_file_write_iter+0xec/0x120 mm/filemap.c:4015
 generic_file_write_iter+0x7d/0x1c0 mm/filemap.c:4044
 do_iter_write+0x4b4/0x7b0 fs/read_write.c:860
 vfs_writev+0x1a8/0x320 fs/read_write.c:933
 do_pwritev fs/read_write.c:1030 [inline]
 __do_sys_pwritev2 fs/read_write.c:1089 [inline]
 __se_sys_pwritev2+0x10c/0x1d0 fs/read_write.c:1080
 __x64_sys_pwritev2+0x78/0x90 fs/read_write.c:1080
 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 0xffff88811cde7000 of 1377 bytes by task 6239 on cpu 0:
 instrument_copy_to_user include/linux/instrumented.h:113 [inline]
 copyout lib/iov_iter.c:167 [inline]
 _copy_to_iter+0x12b/0x910 lib/iov_iter.c:316
 copy_page_to_iter+0x184/0x2c0 lib/iov_iter.c:481
 copy_folio_to_iter include/linux/uio.h:185 [inline]
 filemap_read+0x421/0x670 mm/filemap.c:2709
 blkdev_read_iter+0x217/0x2c0 block/fops.c:617
 call_read_iter include/linux/fs.h:1871 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x3da/0x5c0 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: 0 PID: 6239 Comm: udevd Not tainted 6.5.0-rc7-syzkaller-00013-g53663f4103ff #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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