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BUG: KCSAN: data-race in vm_area_dup / vma_interval_tree_insert_after

write to 0xffff888122b5b6a8 of 8 bytes by task 7671 on cpu 0:
 rb_link_node include/linux/rbtree.h:75 [inline]
 vma_interval_tree_insert_after+0x135/0x170 mm/interval_tree.c:56
 dup_mmap kernel/fork.c:573 [inline]
 dup_mm+0x53e/0xba0 kernel/fork.c:1361
 copy_mm kernel/fork.c:1417 [inline]
 copy_process+0x36f3/0x3b50 kernel/fork.c:2012
 _do_fork+0xfe/0x6e0 kernel/fork.c:2366
 __do_sys_clone kernel/fork.c:2521 [inline]
 __se_sys_clone kernel/fork.c:2502 [inline]
 __x64_sys_clone+0x12b/0x160 kernel/fork.c:2502
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888122b5b640 of 200 bytes by task 7670 on cpu 1:
 vm_area_dup+0x70/0xf0 kernel/fork.c:359
 dup_mmap kernel/fork.c:541 [inline]
 dup_mm+0x330/0xba0 kernel/fork.c:1361
 copy_mm kernel/fork.c:1417 [inline]
 copy_process+0x36f3/0x3b50 kernel/fork.c:2012
 _do_fork+0xfe/0x6e0 kernel/fork.c:2366
 __do_sys_clone kernel/fork.c:2521 [inline]
 __se_sys_clone kernel/fork.c:2502 [inline]
 __x64_sys_clone+0x12b/0x160 kernel/fork.c:2502
 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: 1 PID: 7670 Comm: net.agent 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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