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WARNING: lock held when returning to user space!
syzkaller #0 Tainted: G             L     
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syz.4.5868/25813 is leaving the kernel with locks still held!
2 locks held by syz.4.5868/25813:
 #0: ffff88806504b308 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:310
 #1: ffff88807c9501f0 (&ctx->map_changing_lock){++++}-{4:4}, at: mfill_get_vma+0x162/0x660 mm/userfaultfd.c:226