bpf: offload: don't use prog->aux->offload as boolean

We currently use aux->offload to indicate that program is bound
to a specific device.  This forces us to keep the offload structure
around even after the device is gone.  Add a bool member to
struct bpf_prog_aux to indicate if offload was requested.
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/linux/bpf.h

@@ -201,6 +201,7 @@ struct bpf_prog_aux {
 	u32 stack_depth;
 	u32 id;
 	u32 func_cnt;
+	bool offload_requested;
 	struct bpf_prog **func;
 	void *jit_data; /* JIT specific data. arch dependent */
 	struct latch_tree_node ksym_tnode;
@@ -529,7 +530,7 @@ int bpf_prog_offload_init(struct bpf_prog *prog, union bpf_attr *attr);
 
 static inline bool bpf_prog_is_dev_bound(struct bpf_prog_aux *aux)
 {
-	return aux->offload;
+	return aux->offload_requested;
 }
 #else
 static inline int bpf_prog_offload_init(struct bpf_prog *prog,

kernel/bpf/syscall.c

@@ -1157,6 +1157,8 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (!prog)
 		return -ENOMEM;
 
+	prog->aux->offload_requested = !!attr->prog_ifindex;
+
 	err = security_bpf_prog_alloc(prog->aux);
 	if (err)
 		goto free_prog_nouncharge;
@@ -1178,7 +1180,7 @@ static int bpf_prog_load(union bpf_attr *attr)
 	atomic_set(&prog->aux->refcnt, 1);
 	prog->gpl_compatible = is_gpl ? 1 : 0;
 
-	if (attr->prog_ifindex) {
+	if (bpf_prog_is_dev_bound(prog->aux)) {
 		err = bpf_prog_offload_init(prog, attr);
 		if (err)
 			goto free_prog;