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BUG: KCSAN: data-race in fat_time_unix2fat / fat_truncate_time

read to 0xffff888128ae3220 of 8 bytes by task 20847 on cpu 0:
 fat_time_unix2fat+0x99/0x2c0 fs/fat/misc.c:238
 __fat_write_inode+0x507/0x520 fs/fat/inode.c:885
 fat_write_inode+0x6d/0xf0 fs/fat/inode.c:908
 write_inode fs/fs-writeback.c:1312 [inline]
 __writeback_single_inode+0x6f7/0x8e0 fs/fs-writeback.c:1511
 writeback_single_inode+0x232/0x310 fs/fs-writeback.c:1565
 sync_inode fs/fs-writeback.c:2602 [inline]
 sync_inode_metadata+0x74/0xa0 fs/fs-writeback.c:2622
 __generic_file_fsync+0x122/0x190 fs/libfs.c:1011
 fat_file_fsync+0x58/0x120 fs/fat/file.c:199
 vfs_fsync_range+0x82/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2853 [inline]
 generic_file_write_iter+0x318/0x390 mm/filemap.c:3470
 call_write_iter include/linux/fs.h:1895 [inline]
 do_iter_readv_writev+0x487/0x5b0 fs/read_write.c:693
 do_iter_write fs/read_write.c:970 [inline]
 do_iter_write+0x13b/0x3c0 fs/read_write.c:951
 vfs_iter_write+0x5c/0x80 fs/read_write.c:983
 iter_file_splice_write+0x4c0/0x7f0 fs/splice.c:746
 do_splice_from fs/splice.c:848 [inline]
 direct_splice_actor+0xa0/0xc0 fs/splice.c:1020
 splice_direct_to_actor+0x215/0x510 fs/splice.c:975
 do_splice_direct+0x161/0x1e0 fs/splice.c:1063
 do_sendfile+0x384/0x7f0 fs/read_write.c:1464
 __do_sys_sendfile64 fs/read_write.c:1525 [inline]
 __se_sys_sendfile64 fs/read_write.c:1511 [inline]
 __x64_sys_sendfile64+0x12a/0x140 fs/read_write.c:1511
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888128ae3220 of 8 bytes by task 20848 on cpu 1:
 fat_truncate_time+0x145/0x2e0 fs/fat/misc.c:307
 fat_update_time fs/fat/misc.c:330 [inline]
 fat_update_time+0x75/0x1c0 fs/fat/misc.c:322
 update_time fs/inode.c:1683 [inline]
 touch_atime+0x172/0x190 fs/inode.c:1754
 file_accessed include/linux/fs.h:2202 [inline]
 generic_file_buffered_read mm/filemap.c:2258 [inline]
 generic_file_read_iter+0x116e/0x1440 mm/filemap.c:2324
 call_read_iter include/linux/fs.h:1889 [inline]
 new_sync_read+0x389/0x4f0 fs/read_write.c:414
 __vfs_read+0xb1/0xc0 fs/read_write.c:427
 integrity_kernel_read+0xa1/0xe0 security/integrity/iint.c:200
 ima_calc_file_hash_tfm+0x1b5/0x260 security/integrity/ima/ima_crypto.c:360
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:389 [inline]
 ima_calc_file_hash+0x158/0xf40 security/integrity/ima/ima_crypto.c:454
 ima_collect_measurement+0x3b1/0x3e0 security/integrity/ima/ima_api.c:247
 process_measurement+0x9e3/0x1130 security/integrity/ima/ima_main.c:326
 ima_file_check+0x7e/0xb0 security/integrity/ima/ima_main.c:438
 do_last fs/namei.c:3412 [inline]
 path_openat+0xfaf/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20848 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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