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BUG: KCSAN: data-race in __anon_vma_prepare / handle_mm_fault

write to 0xffff8881270efa48 of 8 bytes by task 8156 on cpu 1:
 __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

read to 0xffff8881270efa48 of 8 bytes by task 8201 on cpu 0:
 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
 user_access_begin arch/x86/include/asm/smap.h:50 [inline]
 filldir+0x1d8/0x3b0 fs/readdir.c:249
 dir_emit_dot include/linux/fs.h:3669 [inline]
 dir_emit_dots include/linux/fs.h:3680 [inline]
 empty_dir_readdir+0x97/0x1a0 fs/libfs.c:1337
 iterate_dir+0x16e/0x370 fs/readdir.c:65
 __do_sys_getdents fs/readdir.c:286 [inline]
 __se_sys_getdents+0x7f/0x190 fs/readdir.c:271
 __x64_sys_getdents+0x3f/0x50 fs/readdir.c:271
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000000000 -> 0xffff88813ad65320

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8201 Comm: syz-executor.3 Tainted: G        W         5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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