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BUG: KCSAN: data-race in vm_area_dup / vma_interval_tree_remove

write to 0xffff888126658cd8 of 8 bytes by task 14302 on cpu 0:
 rb_set_parent include/linux/rbtree_augmented.h:159 [inline]
 __rb_erase_augmented include/linux/rbtree_augmented.h:279 [inline]
 rb_erase_augmented include/linux/rbtree_augmented.h:303 [inline]
 rb_erase_augmented_cached include/linux/rbtree_augmented.h:314 [inline]
 vma_interval_tree_remove+0x315/0x8e0 mm/interval_tree.c:23
 __remove_shared_vm_struct+0xa4/0xc0 mm/mmap.c:151
 unlink_file_vma+0x65/0x80 mm/mmap.c:166
 free_pgtables+0x145/0x1f0 mm/memory.c:414
 exit_mmap+0x14d/0x2f0 mm/mmap.c:3151
 __mmput kernel/fork.c:1085 [inline]
 mmput+0xe2/0x260 kernel/fork.c:1106
 exit_mm kernel/exit.c:479 [inline]
 do_exit+0x644/0x1150 kernel/exit.c:782
 do_group_exit+0xae/0x1a0 kernel/exit.c:893
 __do_sys_exit_group kernel/exit.c:904 [inline]
 __se_sys_exit_group kernel/exit.c:902 [inline]
 __x64_sys_exit_group+0x2b/0x30 kernel/exit.c:902
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888126658c80 of 200 bytes by task 6723 on cpu 1:
 vm_area_dup+0x71/0x110 kernel/fork.c:362
 dup_mmap kernel/fork.c:546 [inline]
 dup_mm+0x337/0xb50 kernel/fork.c:1363
 copy_mm kernel/fork.c:1419 [inline]
 copy_process+0x394f/0x3ab0 kernel/fork.c:2085
 _do_fork+0xf7/0x790 kernel/fork.c:2430
 __do_sys_clone+0xf9/0x130 kernel/fork.c:2585
 __se_sys_clone kernel/fork.c:2566 [inline]
 __x64_sys_clone+0x6c/0x80 kernel/fork.c:2566
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6723 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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