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BUG: KCSAN: data-race in __anon_vma_prepare / handle_mm_fault

write to 0xffff88812eebe208 of 8 bytes by task 18601 on cpu 0:
 __anon_vma_prepare+0x12f/0x2d0 mm/rmap.c:207
 anon_vma_prepare include/linux/rmap.h:152 [inline]
 do_cow_fault mm/memory.c:3996 [inline]
 do_fault mm/memory.c:4110 [inline]
 handle_pte_fault mm/memory.c:4367 [inline]
 __handle_mm_fault mm/memory.c:4502 [inline]
 handle_mm_fault+0x1749/0x1a70 mm/memory.c:4600
 do_user_addr_fault+0x60c/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x94/0x230 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577
 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]
 poll_select_finish+0x2a6/0x3c0 fs/select.c:330
 kern_select fs/select.c:719 [inline]
 __do_sys_select fs/select.c:725 [inline]
 __se_sys_select+0x18f/0x1c0 fs/select.c:722
 __x64_sys_select+0x63/0x70 fs/select.c:722
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812eebe208 of 8 bytes by task 18619 on cpu 1:
 anon_vma_prepare include/linux/rmap.h:149 [inline]
 do_cow_fault mm/memory.c:3996 [inline]
 do_fault mm/memory.c:4110 [inline]
 handle_pte_fault mm/memory.c:4367 [inline]
 __handle_mm_fault mm/memory.c:4502 [inline]
 handle_mm_fault+0xb6a/0x1a70 mm/memory.c:4600
 do_user_addr_fault+0x60c/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x94/0x230 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577
 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]
 poll_select_finish+0x2a6/0x3c0 fs/select.c:330
 kern_select fs/select.c:719 [inline]
 __do_sys_select fs/select.c:725 [inline]
 __se_sys_select+0x18f/0x1c0 fs/select.c:722
 __x64_sys_select+0x63/0x70 fs/select.c:722
 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: 18619 Comm: syz-executor.3 Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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