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BUG: KCSAN: data-race in do_fcntl / generic_write_checks

write to 0xffff888108fc4f40 of 4 bytes by task 22613 on cpu 0:
 setfl fs/fcntl.c:81 [inline]
 do_fcntl+0xbce/0xc30 fs/fcntl.c:355
 __do_sys_fcntl fs/fcntl.c:471 [inline]
 __se_sys_fcntl+0xc6/0x180 fs/fcntl.c:456
 __x64_sys_fcntl+0x3f/0x50 fs/fcntl.c:456
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888108fc4f40 of 4 bytes by task 22662 on cpu 1:
 generic_write_check_limits fs/read_write.c:1624 [inline]
 generic_write_checks+0x1e7/0x290 fs/read_write.c:1663
 generic_file_write_iter+0x58/0x130 mm/filemap.c:3819
 call_write_iter include/linux/fs.h:2114 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x773/0xda0 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22662 Comm: syz-executor.5 Not tainted 5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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