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BUG: KCSAN: data-race in _copy_to_iter / fat16_ent_put

write to 0xffff8881271f5264 of 2 bytes by task 27785 on cpu 0:
 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
 cont_expand_zero fs/buffer.c:2524 [inline]
 cont_write_begin+0x18f/0x6f0 fs/buffer.c:2587
 fat_write_begin+0x61/0xf0 fs/fat/inode.c:230
 generic_cont_expand_simple+0xad/0x140 fs/buffer.c:2488
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_fallocate+0x182/0x1d0 fs/fat/file.c:301
 vfs_fallocate+0x378/0x3e0 fs/open.c:324
 ksys_fallocate fs/open.c:347 [inline]
 __do_sys_fallocate fs/open.c:355 [inline]
 __se_sys_fallocate fs/open.c:353 [inline]
 __x64_sys_fallocate+0x79/0xc0 fs/open.c:353
 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 0xffff8881271f5000 of 1377 bytes by task 19975 on cpu 1:
 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: 1 PID: 19975 Comm: udevd Not tainted 6.5.0-rc6-syzkaller-00225-gaa9ea98cca3a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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