Re: [PATCH v2 5/5] qom/object: Limit type names to alphanumerical and some few special characters

[Daniel P . Berrangé]

On Thu, Nov 16, 2023 at 02:14:54PM +0100, Thomas Huth wrote:
> 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.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  qom/object.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/qom/object.c b/qom/object.c
> index 95c0dc8285..571ef68950 100644
> --- a/qom/object.c
> +++ b/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);
> +
> +    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;
> +    }
> +
> +    for (int i = 1; i < slen; i++) {
> +        if (name[i] != '-' && name[i] != '_' && name[i] != '.' &&
> +            !g_ascii_isalnum(name[i])) {
> +            if (name[i] == '+') {
> +                if (i == 6 && !strncmp(name, "power", 5)) {
> +                    /* It's a legacy name like "power5+" */
> +                    continue;
> +                }
> +                if (i >= 17 && !strncmp(name, "Sun-UltraSparc", 14)) {
> +                    /* It's a legacy name like "Sun-UltraSparc-IV+" */
> +                    continue;
> +                }
> +            }
> +            return false;
> +        }
> +    }

Replace this big loop with strspn, which has an asm optimized impl
in glibc

      ALPHA_LC "abcdefghijklmnopqrstuvwxyz"
      ALPHA_UC "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
      OTHER "0123456789-_."

      return (strspn(name, ALPHA_UC ALPHA_LC OTHER) == slen) ||
          (g_str_has_prefix(name, "power") && slen > 6 && name[6] == '+') ||
          (g_str_has_prefix(name, "Sun-UltraSparc") && slen > 17 && name[17] == 
'+');


With regards,
Daniel
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