syzbot

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BUG: KCSAN: data-race in __page_set_anon_rmap / expand_downwards

read to 0xffff88812338b000 of 8 bytes by task 26140 on cpu 0:
 linear_page_index include/linux/pagemap.h:453 [inline]
 __page_set_anon_rmap+0x12f/0x1f0 mm/rmap.c:1066
 page_add_new_anon_rmap+0x148/0x1f0 mm/rmap.c:1189
 do_anonymous_page mm/memory.c:3135 [inline]
 handle_pte_fault mm/memory.c:3943 [inline]
 __handle_mm_fault+0x1be6/0x2e00 mm/memory.c:4075
 handle_mm_fault+0x21b/0x530 mm/memory.c:4112
 faultin_page mm/gup.c:640 [inline]
 __get_user_pages+0x485/0x1130 mm/gup.c:851
 populate_vma_page_range+0xe6/0x100 mm/gup.c:1235
 __mm_populate+0x168/0x2a0 mm/gup.c:1283
 mm_populate include/linux/mm.h:2347 [inline]
 vm_mmap_pgoff+0x181/0x190 mm/util.c:511
 ksys_mmap_pgoff+0x99/0x420 mm/mmap.c:1607
 __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/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812338b000 of 8 bytes by task 26143 on cpu 1:
 expand_downwards+0x5d7/0x9b0 mm/mmap.c:2476
 expand_stack+0x27/0x40 mm/mmap.c:2533
 do_user_addr_fault arch/x86/mm/fault.c:1413 [inline]
 __do_page_fault+0x679/0x8d0 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:1203
 do_strncpy_from_user lib/strncpy_from_user.c:63 [inline]
 strncpy_from_user+0x1eb/0x2b0 lib/strncpy_from_user.c:120
 getname_flags fs/namei.c:149 [inline]
 getname_flags+0xc3/0x380 fs/namei.c:128
 getname+0x23/0x40 fs/namei.c:209
 do_sys_open+0x27f/0x4f0 fs/open.c:1091
 __do_sys_openat fs/open.c:1124 [inline]
 __se_sys_openat fs/open.c:1118 [inline]
 __x64_sys_openat+0x62/0x80 fs/open.c:1118
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26143 Comm: syz-executor.1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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