bpf, net: validate struct_ops when updating value.

Perform all validations when updating values of struct_ops maps. Doing
validation in st_ops->reg() and st_ops->update() is not necessary anymore.
However, tcp_register_congestion_control() has been called in various
places. It still needs to do validations.

Cc: netdev@vger.kernel.org
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240224223418.526631-2-thinker.li@gmail.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/bpf_struct_ops.c

@@ -672,13 +672,14 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 		*(unsigned long *)(udata + moff) = prog->aux->id;
 	}
 
+	if (st_ops->validate) {
+		err = st_ops->validate(kdata);
+		if (err)
+			goto reset_unlock;
+	}
+
 	if (st_map->map.map_flags & BPF_F_LINK) {
 		err = 0;
-		if (st_ops->validate) {
-			err = st_ops->validate(kdata);
-			if (err)
-				goto reset_unlock;
-		}
 		arch_protect_bpf_trampoline(st_map->image, PAGE_SIZE);
 		/* Let bpf_link handle registration & unregistration.
 		 *

net/ipv4/tcp_cong.c

@@ -146,11 +146,7 @@ EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
 int tcp_update_congestion_control(struct tcp_congestion_ops *ca, struct tcp_congestion_ops *old_ca)
 {
 	struct tcp_congestion_ops *existing;
-	int ret;
-
-	ret = tcp_validate_congestion_control(ca);
-	if (ret)
-		return ret;
+	int ret = 0;
 
 	ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));