hmat acpi: Fix out of bounds access due to missing use of indirection

With a numa set up such as

-numa nodeid=0,cpus=0 \
-numa nodeid=1,memdev=mem \
-numa nodeid=2,cpus=1

and appropriate hmat_lb entries the initiator list is correctly
computed and writen to HMAT as 0,2 but then the LB data is accessed
using the node id (here 2), landing outside the entry_list array.

Stash the reverse lookup when writing the initiator list and use
it to get the correct array index index.

Fixes: 4586a2cb83 ("hmat acpi: Build System Locality Latency and Bandwidth Information Structure(s)")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240307160326.31570-3-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/acpi/hmat.c

@@ -78,6 +78,7 @@ static void build_hmat_lb(GArray *table_data, HMAT_LB_Info *hmat_lb,
                           uint32_t *initiator_list)
 {
     int i, index;
+    uint32_t initiator_to_index[MAX_NODES] = {};
     HMAT_LB_Data *lb_data;
     uint16_t *entry_list;
     uint32_t base;
@@ -121,6 +122,8 @@ static void build_hmat_lb(GArray *table_data, HMAT_LB_Info *hmat_lb,
     /* Initiator Proximity Domain List */
     for (i = 0; i < num_initiator; i++) {
         build_append_int_noprefix(table_data, initiator_list[i], 4);
+        /* Reverse mapping for array possitions */
+        initiator_to_index[initiator_list[i]] = i;
     }
 
     /* Target Proximity Domain List */
@@ -132,7 +135,8 @@ static void build_hmat_lb(GArray *table_data, HMAT_LB_Info *hmat_lb,
     entry_list = g_new0(uint16_t, num_initiator * num_target);
     for (i = 0; i < hmat_lb->list->len; i++) {
         lb_data = &g_array_index(hmat_lb->list, HMAT_LB_Data, i);
-        index = lb_data->initiator * num_target + lb_data->target;
+        index = initiator_to_index[lb_data->initiator] * num_target +
+            lb_data->target;
 
         entry_list[index] = (uint16_t)(lb_data->data / hmat_lb->base);
     }