Re: next: x86_64: kunit test crashed and kernel panic

[Alexander Potapenko]

>
> > <4>[   38.796558]  ? kmalloc_memmove_negative_size+0xeb/0x1f0
> > <4>[   38.797376]  ? __pfx_kmalloc_memmove_negative_size+0x10/0x10
>
> Most certainly kmalloc_memmove_negative_size() is related.
> Looks like we fail to intercept the call to memmove() in this test,
> passing -2 to the actual __memmove().

This was introduced by 69d4c0d321869 ("entry, kasan, x86: Disallow
overriding mem*() functions")

There's Marco's "kasan: Emit different calls for instrumentable
memintrinsics", but it doesn't fix the problem for me (looking
closer...), and GCC support is still not there, right?

Failing to intercept memcpy/memset/memmove should normally result in
false negatives, but kmalloc_memmove_negative_size() makes a strong
assumption that KASAN will catch and prevent memmove(dst, src, -2).