bpf: Propagate __user annotations properly

__htab_map_lookup_and_delete_batch() stores a user pointer in the local
variable ubatch and uses that in copy_{from,to}_user(), but ubatch misses a
__user annotation.

So, sparse warns in the various assignments and uses of ubatch:

  kernel/bpf/hashtab.c:1415:24: warning: incorrect type in initializer
    (different address spaces)
  kernel/bpf/hashtab.c:1415:24:    expected void *ubatch
  kernel/bpf/hashtab.c:1415:24:    got void [noderef] __user *

  kernel/bpf/hashtab.c:1444:46: warning: incorrect type in argument 2
    (different address spaces)
  kernel/bpf/hashtab.c:1444:46:    expected void const [noderef] __user *from
  kernel/bpf/hashtab.c:1444:46:    got void *ubatch

  kernel/bpf/hashtab.c:1608:16: warning: incorrect type in assignment
    (different address spaces)
  kernel/bpf/hashtab.c:1608:16:    expected void *ubatch
  kernel/bpf/hashtab.c:1608:16:    got void [noderef] __user *

  kernel/bpf/hashtab.c:1609:26: warning: incorrect type in argument 1
    (different address spaces)
  kernel/bpf/hashtab.c:1609:26:    expected void [noderef] __user *to
  kernel/bpf/hashtab.c:1609:26:    got void *ubatch

Add the __user annotation to repair this chain of propagating __user
annotations in __htab_map_lookup_and_delete_batch().
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20201207123720.19111-1-lukas.bulwahn@gmail.com

kernel/bpf/hashtab.c

@@ -1412,7 +1412,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	void *keys = NULL, *values = NULL, *value, *dst_key, *dst_val;
 	void __user *uvalues = u64_to_user_ptr(attr->batch.values);
 	void __user *ukeys = u64_to_user_ptr(attr->batch.keys);
-	void *ubatch = u64_to_user_ptr(attr->batch.in_batch);
+	void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
 	u32 batch, max_count, size, bucket_size;
 	struct htab_elem *node_to_free = NULL;
 	u64 elem_map_flags, map_flags;