Hello, The juxtaposition with the other bugchecks didn't make it apparent that the this WARN_ON was one line too soon. An app trying to unregister a not-yet-registered range will trigger an _harmless_ false positive WARN_ON. No real app would do that so it went unnoticed during testing. This should be applied on top of 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas") to shut off the false positive warning. Thanks, Andrea Andrea Arcangeli (1): userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered fs/userfaultfd.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)