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BUG: KCSAN: data-race in copy_page_from_iter / copy_page_from_iter

write to 0xffff888121d68000 of 4096 bytes by task 12313 on cpu 1:
 instrument_copy_from_user include/linux/instrumented.h:136 [inline]
 copyin lib/iov_iter.c:167 [inline]
 copy_page_from_iter_iovec lib/iov_iter.c:312 [inline]
 copy_page_from_iter+0x261/0x530 lib/iov_iter.c:851
 process_vm_rw_pages mm/process_vm_access.c:43 [inline]
 process_vm_rw_single_vec+0x294/0x460 mm/process_vm_access.c:117
 process_vm_rw_core mm/process_vm_access.c:215 [inline]
 process_vm_rw+0x347/0x4e0 mm/process_vm_access.c:283
 __do_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:298 [inline]
 __x64_sys_process_vm_writev+0x76/0x90 mm/process_vm_access.c:298
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

write to 0xffff888121d68000 of 4096 bytes by task 12331 on cpu 0:
 instrument_copy_from_user include/linux/instrumented.h:136 [inline]
 copyin lib/iov_iter.c:167 [inline]
 copy_page_from_iter_iovec lib/iov_iter.c:312 [inline]
 copy_page_from_iter+0x261/0x530 lib/iov_iter.c:851
 process_vm_rw_pages mm/process_vm_access.c:43 [inline]
 process_vm_rw_single_vec+0x294/0x460 mm/process_vm_access.c:117
 process_vm_rw_core mm/process_vm_access.c:215 [inline]
 process_vm_rw+0x347/0x4e0 mm/process_vm_access.c:283
 __do_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:298 [inline]
 __x64_sys_process_vm_writev+0x76/0x90 mm/process_vm_access.c:298
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12331 Comm: syz-executor.3 Not tainted 5.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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