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BUG: KCSAN: data-race in _copy_to_iter / fat16_ent_put

write to 0xffff88814dbea37e of 2 bytes by task 26954 on cpu 0:
 fat16_ent_put+0x24/0x50 fs/fat/fatent.c:183
 fat_ent_write+0x5e/0xd0 fs/fat/fatent.c:417
 fat_chain_add+0x15b/0x410 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+0x486/0x600 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:2471
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 cont_expand_zero fs/buffer.c:2398 [inline]
 cont_write_begin+0x1a0/0x520 fs/buffer.c:2461
 fat_write_begin+0x5d/0xe0 fs/fat/inode.c:235
 generic_cont_expand_simple+0xa9/0x140 fs/buffer.c:2362
 fat_cont_expand+0x3a/0x160 fs/fat/file.c:223
 fat_setattr+0x356/0x9b0 fs/fat/file.c:512
 notify_change+0x9f8/0xb20 fs/attr.c:418
 do_truncate fs/open.c:65 [inline]
 do_sys_ftruncate+0x317/0x420 fs/open.c:193
 __do_sys_ftruncate fs/open.c:204 [inline]
 __se_sys_ftruncate fs/open.c:202 [inline]
 __x64_sys_ftruncate+0x2f/0x40 fs/open.c:202
 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+0x63/0xcd

read to 0xffff88814dbea000 of 1377 bytes by task 4293 on cpu 1:
 instrument_copy_to_user include/linux/instrumented.h:119 [inline]
 copyout lib/iov_iter.c:154 [inline]
 _copy_to_iter+0x18c/0x820 lib/iov_iter.c:499
 __copy_page_to_iter lib/iov_iter.c:694 [inline]
 copy_page_to_iter+0x1c6/0x3e0 lib/iov_iter.c:709
 copy_folio_to_iter include/linux/uio.h:153 [inline]
 filemap_read+0x119b/0x1430 mm/filemap.c:2717
 blkdev_read_iter+0x2c6/0x370 block/fops.c:598
 call_read_iter include/linux/fs.h:2182 [inline]
 new_sync_read fs/read_write.c:390 [inline]
 vfs_read+0x3a9/0x570 fs/read_write.c:471
 ksys_read+0xe8/0x1a0 fs/read_write.c:609
 __do_sys_read fs/read_write.c:619 [inline]
 __se_sys_read fs/read_write.c:617 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:617
 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+0x63/0xcd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4293 Comm: udevd Not tainted 5.19.0-syzkaller-09084-gc040862bfbd9-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
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