bpf: bpf_prog_array_alloc() should return a generic non-rcu pointer

Currently the return type of the bpf_prog_array_alloc() is
struct bpf_prog_array __rcu *, which is not quite correct.
Obviously, the returned pointer is a generic pointer, which
is valid for an indefinite amount of time and it's not shared
with anyone else, so there is no sense in marking it as __rcu.

This change eliminate the following sparse warnings:
kernel/bpf/core.c:1544:31: warning: incorrect type in return expression (different address spaces)
kernel/bpf/core.c:1544:31:    expected struct bpf_prog_array [noderef] <asn:4>*
kernel/bpf/core.c:1544:31:    got void *
kernel/bpf/core.c:1548:17: warning: incorrect type in return expression (different address spaces)
kernel/bpf/core.c:1548:17:    expected struct bpf_prog_array [noderef] <asn:4>*
kernel/bpf/core.c:1548:17:    got struct bpf_prog_array *<noident>
kernel/bpf/core.c:1681:15: warning: incorrect type in assignment (different address spaces)
kernel/bpf/core.c:1681:15:    expected struct bpf_prog_array *array
kernel/bpf/core.c:1681:15:    got struct bpf_prog_array [noderef] <asn:4>*

Fixes: 324bda9e ("bpf: multi program support for cgroup+bpf")
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf.h

@@ -352,7 +352,7 @@ struct bpf_prog_array {
 	struct bpf_prog *progs[0];
 };
 
-struct bpf_prog_array __rcu *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
+struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags);
 void bpf_prog_array_free(struct bpf_prog_array __rcu *progs);
 int bpf_prog_array_length(struct bpf_prog_array __rcu *progs);
 int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs,

kernel/bpf/core.c

@@ -1538,7 +1538,7 @@ static struct {
 	.null_prog = NULL,
 };
 
-struct bpf_prog_array __rcu *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags)
+struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags)
 {
 	if (prog_cnt)
 		return kzalloc(sizeof(struct bpf_prog_array) +