hw/smbios: fix field corruption in type 4 table

Since table type 4 of SMBIOS version 2.6 is shorter than 3.0, the
strings which follow immediately after the struct fields have been
overwritten by unconditional filling of later fields such as core_count2.
Make these fields dependent on the SMBIOS version.

Fixes: 05e27d74c7 ("hw/smbios: add core_count2 to smbios table type 4")
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2169904

Signed-off-by: Julia Suvorova <jusual@redhat.com>
Message-Id: <20230223125747.254914-1-jusual@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/smbios/smbios.c

@@ -750,14 +750,16 @@ static void smbios_build_type_4_table(MachineState *ms, unsigned instance)
     t->core_count = (ms->smp.cores > 255) ? 0xFF : ms->smp.cores;
     t->core_enabled = t->core_count;
 
-    t->core_count2 = t->core_enabled2 = cpu_to_le16(ms->smp.cores);
-
     t->thread_count = (ms->smp.threads > 255) ? 0xFF : ms->smp.threads;
-    t->thread_count2 = cpu_to_le16(ms->smp.threads);
 
     t->processor_characteristics = cpu_to_le16(0x02); /* Unknown */
     t->processor_family2 = cpu_to_le16(0x01); /* Other */
 
+    if (tbl_len == SMBIOS_TYPE_4_LEN_V30) {
+        t->core_count2 = t->core_enabled2 = cpu_to_le16(ms->smp.cores);
+        t->thread_count2 = cpu_to_le16(ms->smp.threads);
+    }
+
     SMBIOS_BUILD_TABLE_POST;
     smbios_type4_count++;
 }