bpf: Support consuming XDP HW metadata from fext programs

Instead of rejecting the attaching of PROG_TYPE_EXT programs to XDP
programs that consume HW metadata, implement support for propagating the
offload information. The extension program doesn't need to set a flag or
ifindex, these will just be propagated from the target by the verifier.
We need to create a separate offload object for the extension program,
though, since it can be reattached to a different program later (which
means we can't just inherit the offload information from the target).

An additional check is added on attach that the new target is compatible
with the offload information in the extension prog.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230119221536.3349901-9-sdf@google.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

include/linux/bpf.h

@@ -2484,6 +2484,7 @@ int bpf_dev_bound_kfunc_check(struct bpf_verifier_log *log,
 			      struct bpf_prog_aux *prog_aux);
 void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id);
 int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr);
+int bpf_prog_dev_bound_inherit(struct bpf_prog *new_prog, struct bpf_prog *old_prog);
 void bpf_dev_bound_netdev_unregister(struct net_device *dev);
 
 static inline bool bpf_prog_is_dev_bound(const struct bpf_prog_aux *aux)
@@ -2496,6 +2497,8 @@ static inline bool bpf_prog_is_offloaded(const struct bpf_prog_aux *aux)
 	return aux->offload_requested;
 }
 
+bool bpf_prog_dev_bound_match(const struct bpf_prog *lhs, const struct bpf_prog *rhs);
+
 static inline bool bpf_map_is_offloaded(struct bpf_map *map)
 {
 	return unlikely(map->ops == &bpf_map_offload_ops);
@@ -2535,6 +2538,12 @@ static inline int bpf_prog_dev_bound_init(struct bpf_prog *prog,
 	return -EOPNOTSUPP;
 }
 
+static inline int bpf_prog_dev_bound_inherit(struct bpf_prog *new_prog,
+					     struct bpf_prog *old_prog)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline void bpf_dev_bound_netdev_unregister(struct net_device *dev)
 {
 }
@@ -2549,6 +2558,11 @@ static inline bool bpf_prog_is_offloaded(struct bpf_prog_aux *aux)
 	return false;
 }
 
+static inline bool bpf_prog_dev_bound_match(const struct bpf_prog *lhs, const struct bpf_prog *rhs)
+{
+	return false;
+}
+
 static inline bool bpf_map_is_offloaded(struct bpf_map *map)
 {
 	return false;

kernel/bpf/offload.c

@@ -187,43 +187,24 @@ static void __bpf_offload_dev_netdev_unregister(struct bpf_offload_dev *offdev,
 	kfree(ondev);
 }
 
-int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
+static int __bpf_prog_dev_bound_init(struct bpf_prog *prog, struct net_device *netdev)
 {
 	struct bpf_offload_netdev *ondev;
 	struct bpf_prog_offload *offload;
 	int err;
 
-	if (attr->prog_type != BPF_PROG_TYPE_SCHED_CLS &&
-	    attr->prog_type != BPF_PROG_TYPE_XDP)
-		return -EINVAL;
-
-	if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
-		return -EINVAL;
-
-	if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&
-	    attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY)
-		return -EINVAL;
-
 	offload = kzalloc(sizeof(*offload), GFP_USER);
 	if (!offload)
 		return -ENOMEM;
 
 	offload->prog = prog;
+	offload->netdev = netdev;
 
-	offload->netdev = dev_get_by_index(current->nsproxy->net_ns,
-					   attr->prog_ifindex);
-	err = bpf_dev_offload_check(offload->netdev);
-	if (err)
-		goto err_maybe_put;
-
-	prog->aux->offload_requested = !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY);
-
-	down_write(&bpf_devs_lock);
 	ondev = bpf_offload_find_netdev(offload->netdev);
 	if (!ondev) {
 		if (bpf_prog_is_offloaded(prog->aux)) {
 			err = -EINVAL;
-			goto err_unlock;
+			goto err_free;
 		}
 
 		/* When only binding to the device, explicitly
@@ -231,25 +212,80 @@ int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
 		 */
 		err = __bpf_offload_dev_netdev_register(NULL, offload->netdev);
 		if (err)
-			goto err_unlock;
+			goto err_free;
 		ondev = bpf_offload_find_netdev(offload->netdev);
 	}
 	offload->offdev = ondev->offdev;
 	prog->aux->offload = offload;
 	list_add_tail(&offload->offloads, &ondev->progs);
-	dev_put(offload->netdev);
-	up_write(&bpf_devs_lock);
 
 	return 0;
-err_unlock:
-	up_write(&bpf_devs_lock);
-err_maybe_put:
-	if (offload->netdev)
-		dev_put(offload->netdev);
+err_free:
 	kfree(offload);
 	return err;
 }
 
+int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
+{
+	struct net_device *netdev;
+	int err;
+
+	if (attr->prog_type != BPF_PROG_TYPE_SCHED_CLS &&
+	    attr->prog_type != BPF_PROG_TYPE_XDP)
+		return -EINVAL;
+
+	if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
+		return -EINVAL;
+
+	if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&
+	    attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY)
+		return -EINVAL;
+
+	netdev = dev_get_by_index(current->nsproxy->net_ns, attr->prog_ifindex);
+	if (!netdev)
+		return -EINVAL;
+
+	err = bpf_dev_offload_check(netdev);
+	if (err)
+		goto out;
+
+	prog->aux->offload_requested = !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY);
+
+	down_write(&bpf_devs_lock);
+	err = __bpf_prog_dev_bound_init(prog, netdev);
+	up_write(&bpf_devs_lock);
+
+out:
+	dev_put(netdev);
+	return err;
+}
+
+int bpf_prog_dev_bound_inherit(struct bpf_prog *new_prog, struct bpf_prog *old_prog)
+{
+	int err;
+
+	if (!bpf_prog_is_dev_bound(old_prog->aux))
+		return 0;
+
+	if (bpf_prog_is_offloaded(old_prog->aux))
+		return -EINVAL;
+
+	new_prog->aux->dev_bound = old_prog->aux->dev_bound;
+	new_prog->aux->offload_requested = old_prog->aux->offload_requested;
+
+	down_write(&bpf_devs_lock);
+	if (!old_prog->aux->offload) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = __bpf_prog_dev_bound_init(new_prog, old_prog->aux->offload->netdev);
+
+out:
+	up_write(&bpf_devs_lock);
+	return err;
+}
+
 int bpf_prog_offload_verifier_prep(struct bpf_prog *prog)
 {
 	struct bpf_prog_offload *offload;
@@ -675,6 +711,22 @@ bool bpf_offload_dev_match(struct bpf_prog *prog, struct net_device *netdev)
 }
 EXPORT_SYMBOL_GPL(bpf_offload_dev_match);
 
+bool bpf_prog_dev_bound_match(const struct bpf_prog *lhs, const struct bpf_prog *rhs)
+{
+	bool ret;
+
+	if (bpf_prog_is_offloaded(lhs->aux) != bpf_prog_is_offloaded(rhs->aux))
+		return false;
+
+	down_read(&bpf_devs_lock);
+	ret = lhs->aux->offload && rhs->aux->offload &&
+	      lhs->aux->offload->netdev &&
+	      lhs->aux->offload->netdev == rhs->aux->offload->netdev;
+	up_read(&bpf_devs_lock);
+
+	return ret;
+}
+
 bool bpf_offload_prog_map_match(struct bpf_prog *prog, struct bpf_map *map)
 {
 	struct bpf_offloaded_map *offmap;

kernel/bpf/syscall.c

@@ -2605,6 +2605,13 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
 			goto free_prog_sec;
 	}
 
+	if (type == BPF_PROG_TYPE_EXT && dst_prog &&
+	    bpf_prog_is_dev_bound(dst_prog->aux)) {
+		err = bpf_prog_dev_bound_inherit(prog, dst_prog);
+		if (err)
+			goto free_prog_sec;
+	}
+
 	/* find program type: socket_filter vs tracing_filter */
 	err = find_prog_type(type, prog);
 	if (err < 0)

kernel/bpf/verifier.c

@@ -16813,8 +16813,9 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
 	if (tgt_prog) {
 		struct bpf_prog_aux *aux = tgt_prog->aux;
 
-		if (bpf_prog_is_dev_bound(tgt_prog->aux)) {
-			bpf_log(log, "Replacing device-bound programs not supported\n");
+		if (bpf_prog_is_dev_bound(prog->aux) &&
+		    !bpf_prog_dev_bound_match(prog, tgt_prog)) {
+			bpf_log(log, "Target program bound device mismatch");
 			return -EINVAL;
 		}