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BUG: KCSAN: data-race in __anon_vma_prepare / handle_mm_fault

write to 0xffff888158aaeb08 of 8 bytes by task 558 on cpu 0:
 __anon_vma_prepare+0x12f/0x2d0 mm/rmap.c:207
 anon_vma_prepare include/linux/rmap.h:149 [inline]
 do_cow_fault mm/memory.c:4188 [inline]
 do_fault mm/memory.c:4302 [inline]
 handle_pte_fault mm/memory.c:4558 [inline]
 __handle_mm_fault mm/memory.c:4693 [inline]
 handle_mm_fault+0x1729/0x1a50 mm/memory.c:4791
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x91/0x220 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:568
 __put_user_nocheck_4+0x3/0x11
 __sys_socketpair+0xb2/0x800 net/socket.c:1588
 __do_sys_socketpair net/socket.c:1654 [inline]
 __se_sys_socketpair net/socket.c:1651 [inline]
 __x64_sys_socketpair+0x4e/0x60 net/socket.c:1651
 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

read to 0xffff888158aaeb08 of 8 bytes by task 575 on cpu 1:
 anon_vma_prepare include/linux/rmap.h:146 [inline]
 do_cow_fault mm/memory.c:4188 [inline]
 do_fault mm/memory.c:4302 [inline]
 handle_pte_fault mm/memory.c:4558 [inline]
 __handle_mm_fault mm/memory.c:4693 [inline]
 handle_mm_fault+0xb4a/0x1a50 mm/memory.c:4791
 do_user_addr_fault+0x609/0xbe0 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x91/0x220 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:568
 copy_user_generic_unrolled+0x89/0xc0 arch/x86/lib/copy_user_64.S:91
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:58 [inline]
 _copy_to_user+0x77/0x90 lib/usercopy.c:33
 copy_to_user include/linux/uaccess.h:200 [inline]
 do_pipe2+0x60/0xf0 fs/pipe.c:1009
 __do_sys_pipe fs/pipe.c:1030 [inline]
 __se_sys_pipe fs/pipe.c:1028 [inline]
 __x64_sys_pipe+0x1d/0x30 fs/pipe.c:1028
 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

value changed: 0x0000000000000000 -> 0xffff888156fe3910

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 575 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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