syzbot

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BUG: KCSAN: data-race in expand_downwards / find_vma

write to 0xffff88809a6f2d48 of 8 bytes by task 13216 on cpu 0:
 expand_downwards+0x5d7/0x9b0 mm/mmap.c:2466
 expand_stack+0x27/0x40 mm/mmap.c:2523
 do_user_addr_fault arch/x86/mm/fault.c:1414 [inline]
 do_page_fault+0x6c8/0xa3d arch/x86/mm/fault.c:1517
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1203
 do_strncpy_from_user lib/strncpy_from_user.c:40 [inline]
 strncpy_from_user+0x18b/0x2d0 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_openat2+0x396/0x620 fs/open.c:1143
 do_sys_open+0xa3/0x110 fs/open.c:1165
 __do_sys_openat fs/open.c:1179 [inline]
 __se_sys_openat fs/open.c:1174 [inline]
 __x64_sys_openat+0x62/0x80 fs/open.c:1174
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809a6f2d48 of 8 bytes by task 13212 on cpu 1:
 find_vma+0x75/0x110 mm/mmap.c:2232
 __mm_populate+0x1e7/0x2a0 mm/gup.c:1210
 mm_populate include/linux/mm.h:2343 [inline]
 vm_mmap_pgoff+0x181/0x190 mm/util.c:511
 ksys_mmap_pgoff+0x99/0x420 mm/mmap.c:1597
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:99 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:90 [inline]
 __x64_sys_mmap+0x2e/0x40 arch/x86/kernel/sys_x86_64.c:90
 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: 13212 Comm: syz-executor.1 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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