Merge branch 'bpf-fix-null-deref-when-storing-scalar-into-kptr-slot'

Mykyta Yatsenko says:

====================
bpf: Fix NULL deref when storing scalar into kptr slot

map_kptr_match_type() accesses reg->btf before confirming the register
is PTR_TO_BTF_ID. A scalar store into a kptr slot has no btf, causing
a NULL pointer dereference. Guard base_type() first.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
====================

Link: https://patch.msgid.link/20260416-kptr_crash-v1-0-5589356584b4@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>