syzbot

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BUG: KCSAN: data-race in filemap_fault / filemap_fault

write to 0xffff8881070199a4 of 4 bytes by task 15023 on cpu 1:
 do_sync_mmap_readahead mm/filemap.c:2442 [inline]
 filemap_fault+0xd8a/0xf90 mm/filemap.c:2529
 ext4_filemap_fault+0x59/0x72 fs/ext4/inode.c:6292
 __do_fault+0xae/0x1f0 mm/memory.c:3092
 do_shared_fault mm/memory.c:3544 [inline]
 do_fault mm/memory.c:3622 [inline]
 handle_pte_fault mm/memory.c:3849 [inline]
 __handle_mm_fault+0x2019/0x2c70 mm/memory.c:3973
 handle_mm_fault+0x21b/0x530 mm/memory.c:4010
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x456/0x8d0 arch/x86/mm/fault.c:1506
 do_page_fault+0x38/0x194 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1202

write to 0xffff8881070199a4 of 4 bytes by task 15024 on cpu 0:
 do_sync_mmap_readahead mm/filemap.c:2442 [inline]
 filemap_fault+0xd8a/0xf90 mm/filemap.c:2529
 ext4_filemap_fault+0x59/0x72 fs/ext4/inode.c:6292
 __do_fault+0xae/0x1f0 mm/memory.c:3092
 do_read_fault mm/memory.c:3489 [inline]
 do_fault mm/memory.c:3618 [inline]
 handle_pte_fault mm/memory.c:3849 [inline]
 __handle_mm_fault+0x1f90/0x2c70 mm/memory.c:3973
 handle_mm_fault+0x21b/0x530 mm/memory.c:4010
 faultin_page mm/gup.c:640 [inline]
 __get_user_pages+0x485/0x1160 mm/gup.c:845
 populate_vma_page_range+0xe6/0x100 mm/gup.c:1223
 __mm_populate+0x168/0x2a0 mm/gup.c:1271
 mm_populate include/linux/mm.h:2357 [inline]
 vm_mmap_pgoff+0x181/0x190 mm/util.c:501
 ksys_mmap_pgoff+0x2d8/0x420 mm/mmap.c:1629
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0x2e/0x40 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 15024 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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