bpf: Initialize storage pointers to NULL to prevent freeing garbage pointer

bpf: Initialize storage pointers to NULL to prevent freeing garbage pointer

commit 0da6e9fb26b2b99128d5f3a1b8b356c6d00b505d upstream.

Local storage array isn't initialized, so if cgroup storage allocation fails
for BPF_CGROUP_STORAGE_SHARED, error handling code will attempt to free
uninitialized pointer for BPF_CGROUP_STORAGE_PERCPU storage type. Avoid this
by always initializing storage pointers to NULLs.

Fixes: 6f317e33a148 ("bpf: extend cgroup bpf core to allow multiple cgroup storage types")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200309222756.1018737-1-andriin@fb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>