6394 ::mac_flow -s segfaults
Reviewed by: Jason King <jason.brian.king@gmail.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>

@@ -326,26 +326,46 @@
         }
         case MAC_FLOW_STATS: {
                 uint64_t                totibytes = 0;
                 uint64_t                totobytes = 0;
                 mac_soft_ring_set_t     *mac_srs;
-                mac_rx_stats_t          *mac_rx_stat;
-                mac_tx_stats_t          *mac_tx_stat;
+                mac_rx_stats_t          mac_rx_stat;
+                mac_tx_stats_t          mac_tx_stat;
                 int                     i;
 
+                /*
+                 * Sum bytes for all Rx SRS.
+                 */
                 for (i = 0; i < fe.fe_rx_srs_cnt; i++) {
                         mac_srs = (mac_soft_ring_set_t *)(fe.fe_rx_srs[i]);
-                        mac_rx_stat = &mac_srs->srs_rx.sr_stat;
-                        totibytes += mac_rx_stat->mrs_intrbytes +
-                            mac_rx_stat->mrs_pollbytes +
-                            mac_rx_stat->mrs_lclbytes;
+                        if (mdb_vread(&mac_rx_stat, sizeof (mac_rx_stats_t),
+                            (uintptr_t)&mac_srs->srs_rx.sr_stat) == -1) {
+                                mdb_warn("failed to read mac_rx_stats_t at %p",
+                                    &mac_srs->srs_rx.sr_stat);
+                                return (DCMD_ERR);
                 }
+
+                        totibytes += mac_rx_stat.mrs_intrbytes +
+                            mac_rx_stat.mrs_pollbytes +
+                            mac_rx_stat.mrs_lclbytes;
+                }
+
+                /*
+                 * Sum bytes for Tx SRS.
+                 */
                 mac_srs = (mac_soft_ring_set_t *)(fe.fe_tx_srs);
                 if (mac_srs != NULL) {
-                        mac_tx_stat = &mac_srs->srs_tx.st_stat;
-                        totobytes = mac_tx_stat->mts_obytes;
+                        if (mdb_vread(&mac_tx_stat, sizeof (mac_tx_stats_t),
+                            (uintptr_t)&mac_srs->srs_tx.st_stat) == -1) {
+                                mdb_warn("failed to read max_tx_stats_t at %p",
+                                    &mac_srs->srs_tx.st_stat);
+                                return (DCMD_ERR);
                 }
+
+                        totobytes = mac_tx_stat.mts_obytes;
+                }
+
                 mdb_printf("%?p %-32s %16llu %16llu\n",
                     addr, fe.fe_flow_name, totibytes, totobytes);
 
                 break;
         }