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BUG: KCSAN: data-race in do_sendfile / ksys_write

write to 0xffff88813f6b4c68 of 8 bytes by task 21096 on cpu 1:
 do_sendfile+0x915/0xc40 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1304 [inline]
 __se_sys_sendfile64 fs/read_write.c:1296 [inline]
 __x64_sys_sendfile64+0xb9/0x140 fs/read_write.c:1296
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813f6b4c68 of 8 bytes by task 21093 on cpu 0:
 ksys_write+0x9c/0x190 fs/read_write.c:640
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000000000aa88 -> 0x000000000000a1a0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21093 Comm: syz-executor.2 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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