3027 installgrub can segfault when encountering bogus data on disk

@@ -401,11 +401,11 @@
                     device_path);
                 retval = BC_NOEINFO;
                 goto out_dev;
         }
 
-        einfo = find_einfo(stage2->extra);
+        einfo = find_einfo(stage2->extra, stage2->extra_size);
         if (einfo == NULL) {
                 retval = BC_NOEINFO;
                 (void) fprintf(stderr, gettext("No extended information "
                     "found\n"));
                 goto out_dev;

@@ -499,11 +499,11 @@
                     "stage2\n", curr_device->path);
                 retval = BC_NOEXTRA;
                 goto out_devs;
         }
 
-        einfo_curr = find_einfo(stage2_curr->extra);
+        einfo_curr = find_einfo(stage2_curr->extra, stage2_curr->extra_size);
         if (einfo_curr != NULL)
                 updt_str = einfo_get_string(einfo_curr);
 
         write_mbr = B_TRUE;
         force_mbr = B_TRUE;

@@ -1219,10 +1219,11 @@
         stage2->file = stage2->buf;
         stage2->file_size = size;
         stage2->mboot_off = mboot_off;
         stage2->mboot = (multiboot_header_t *)(stage2->buf + stage2->mboot_off);
         stage2->extra = stage2->buf + P2ROUNDUP(stage2->file_size, 8);
+        stage2->extra_size = stage2->buf_size - P2ROUNDUP(stage2->file_size, 8);
 
         return (BC_SUCCESS);
 }
 
 static boolean_t

@@ -1249,11 +1250,11 @@
 
         /*
          * Look for the extended information structure in the extra payload
          * area.
          */
-        einfo = find_einfo(stage2_disk.extra);
+        einfo = find_einfo(stage2_disk.extra, stage2_disk.extra_size);
         if (einfo == NULL) {
                 BOOT_DEBUG("No extended information available\n");
                 return (B_TRUE);
         }