syzbot reported an illegal copy_to_user() attempt
from bpf_prog_get_info_by_fd() [1]
There was no repro yet on this bug, but I think
that commit 0aef499f3172 ("mm/usercopy: Detect vmalloc overruns")
is exposing a prior bug in bpf arm64.
bpf_prog_get_info_by_fd() looks at prog->jited_len
to determine if the JIT image can be copied out to user space.
My theory is that syzbot managed to get a prog where prog->jited_len
has been set to 43, while prog->bpf_func has ben cleared.
It is not clear why copy_to_user(uinsns, NULL, ulen) is triggering
this particular warning.
I thought find_vma_area(NULL) would not find a vm_struct.
As we do not hold vmap_area_lock spinlock, it might be possible
that the found vm_struct was garbage.