safe slice operation (#5471)

substrate/frame/support/src/hash.rs

@@ -92,6 +92,10 @@ impl StorageHasher for Twox64Concat {
 }
 impl ReversibleStorageHasher for Twox64Concat {
 	fn reverse(x: &[u8]) -> &[u8] {
+		if x.len() < 8 {
+			crate::debug::error!("Invalid reverse: hash length too short");
+			return &[]
+		}
 		&x[8..]
 	}
 }
@@ -110,6 +114,10 @@ impl StorageHasher for Blake2_128Concat {
 }
 impl ReversibleStorageHasher for Blake2_128Concat {
 	fn reverse(x: &[u8]) -> &[u8] {
+		if x.len() < 16 {
+			crate::debug::error!("Invalid reverse: hash length too short");
+			return &[]
+		}
 		&x[16..]
 	}
 }