==================================================================
BUG: KCSAN: data-race in copyout / fat16_ent_put

write to 0xffff88811ca48fbc of 2 bytes by task 20077 on cpu 1:
 fat16_ent_put+0x5b/0x90 fs/fat/fatent.c:181
 fat_alloc_clusters+0x507/0xc40 fs/fat/fatent.c:501
 fat_add_cluster+0x3d/0xd0 fs/fat/inode.c:108
 __fat_get_block fs/fat/inode.c:155 [inline]
 fat_get_block+0x3ae/0x4e0 fs/fat/inode.c:190
 __block_write_begin_int+0x2ea/0xf10 fs/buffer.c:2008
 __block_write_begin fs/buffer.c:2058 [inline]
 block_write_begin+0x77/0x160 fs/buffer.c:2117
 cont_write_begin+0x3d6/0x670 fs/buffer.c:2466
 fat_write_begin+0x72/0xc0 fs/fat/inode.c:236
 pagecache_write_begin+0x6b/0x90 mm/filemap.c:3106
 cont_expand_zero fs/buffer.c:2393 [inline]
 cont_write_begin+0x17a/0x670 fs/buffer.c:2456
 fat_write_begin+0x72/0xc0 fs/fat/inode.c:236
 pagecache_write_begin+0x6b/0x90 mm/filemap.c:3106
 generic_cont_expand_simple+0xb0/0x120 fs/buffer.c:2357
 fat_cont_expand+0x4e/0x1c0 fs/fat/file.c:222
 fat_fallocate+0x1af/0x1f0 fs/fat/file.c:300
 vfs_fallocate+0x3be/0x650 fs/open.c:309
 ksys_fallocate+0x61/0xa0 fs/open.c:332
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0x5e/0x80 fs/open.c:338
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811ca48c00 of 1024 bytes by task 20079 on cpu 0:
 instrument_copy_to_user include/linux/instrumented.h:89 [inline]
 copyout+0xa8/0xc0 lib/iov_iter.c:142
 copy_page_to_iter_iovec lib/iov_iter.c:212 [inline]
 copy_page_to_iter+0x252/0x8e0 lib/iov_iter.c:921
 generic_file_buffered_read mm/filemap.c:2122 [inline]
 generic_file_read_iter+0x978/0x1440 mm/filemap.c:2302
 blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2039
 call_read_iter include/linux/fs.h:1895 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414
 __vfs_read+0xb1/0xc0 fs/read_write.c:427
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0xd5/0x1b0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x4c/0x60 fs/read_write.c:595
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20079 Comm: blkid Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================