qom/object: Limit type names to alphanumerical and some few special characters

QOM names currently don't have any enforced naming rules. This
can be problematic, e.g. when they are used on the command line
for the "-device" option (where the comma is used to separate
properties). To avoid that such problematic type names come in
again, let's restrict the set of acceptable characters during the
type registration.

Ideally, we'd apply here the same rules as for QAPI, i.e. all type
names should begin with a letter, and contain only ASCII letters,
digits, hyphen, and underscore. However, we already have so many
pre-existing types like:

    486-x86_64-cpu
    cfi.pflash01
    power5+_v2.1-spapr-cpu-core
    virt-2.6-machine
    pc-i440fx-3.0-machine

... so that we have to allow "." and "+" for now, too. While the
dot is used in a lot of places, the "+" can fortunately be limited
to two classes of legacy names ("power" and "Sun-UltraSparc" CPUs).

We also cannot enforce the rule that names must start with a letter
yet, since there are lot of types that start with a digit. Still,
at least limiting the first characters to the alphanumerical range
should be way better than nothing.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231117114457.177308-6-thuth@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

qom/object.c

@@ -138,9 +138,50 @@ static TypeImpl *type_new(const TypeInfo *info)
     return ti;
 }
 
+static bool type_name_is_valid(const char *name)
+{
+    const int slen = strlen(name);
+    int plen;
+
+    g_assert(slen > 1);
+
+    /*
+     * Ideally, the name should start with a letter - however, we've got
+     * too many names starting with a digit already, so allow digits here,
+     * too (except '0' which is not used yet)
+     */
+    if (!g_ascii_isalnum(name[0]) || name[0] == '0') {
+        return false;
+    }
+
+    plen = strspn(name, "abcdefghijklmnopqrstuvwxyz"
+                        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+                        "0123456789-_.");
+
+    /* Allow some legacy names with '+' in it for compatibility reasons */
+    if (name[plen] == '+') {
+        if (plen == 6 && g_str_has_prefix(name, "power")) {
+            /* Allow "power5+" and "power7+" CPU names*/
+            return true;
+        }
+        if (plen >= 17 && g_str_has_prefix(name, "Sun-UltraSparc-I")) {
+            /* Allow "Sun-UltraSparc-IV+" and "Sun-UltraSparc-IIIi+" */
+            return true;
+        }
+    }
+
+    return plen == slen;
+}
+
 static TypeImpl *type_register_internal(const TypeInfo *info)
 {
     TypeImpl *ti;
+
+    if (!type_name_is_valid(info->name)) {
+        fprintf(stderr, "Registering '%s' with illegal type name\n", info->name);
+        abort();
+    }
+
     ti = type_new(info);
 
     type_table_add(ti);