diff --git a/elf/dl-misc.c b/elf/dl-misc.c
index 5b84adc2f4..8dccb3a9a9 100644
--- a/elf/dl-misc.c
+++ b/elf/dl-misc.c
@@ -174,6 +174,9 @@ _dl_strtoul (const char *nptr, char **endptr)
       return 0UL;
     }
 
+  uint64_t cutoff = (UINT64_MAX * 2UL + 1UL) / 10;
+  uint64_t cutlim = (UINT64_MAX * 2UL + 1UL) % 10;
+
   int base = 10;
   max_digit = 9;
   if (*nptr == '0')
@@ -182,14 +185,19 @@ _dl_strtoul (const char *nptr, char **endptr)
 	{
 	  base = 16;
 	  nptr += 2;
+	  cutoff = (UINT64_MAX * 2UL + 1UL) / 16;
+	  cutlim = (UINT64_MAX * 2UL + 1UL) % 16;
 	}
       else
 	{
 	  base = 8;
 	  max_digit = 7;
+	  cutoff = (UINT64_MAX * 2UL + 1UL) / 8;
+	  cutlim = (UINT64_MAX * 2UL + 1UL) % 8;
 	}
     }
 
+
   while (1)
     {
       int digval;
@@ -207,7 +215,7 @@ _dl_strtoul (const char *nptr, char **endptr)
       else
         break;
 
-      if (result >= (UINT64_MAX - digval) / base)
+      if (result > cutoff || (result == cutoff && digval > cutlim))
 	{
 	  if (endptr != NULL)
 	    *endptr = (char *) nptr;
diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
index 3d41e8e28e..092b696484 100644
--- a/elf/dl-tunables.c
+++ b/elf/dl-tunables.c
@@ -69,16 +69,27 @@ do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
 {
   tunable_num_t val, min, max;
 
-  if (cur->type.type_code == TUNABLE_TYPE_STRING)
+  switch (cur->type.type_code)
     {
+    case TUNABLE_TYPE_STRING:
       cur->val.strval = valp->strval;
       cur->initialized = true;
       return;
+    case TUNABLE_TYPE_INT_32:
+      val = (int32_t) valp->numval;
+      break;
+    case TUNABLE_TYPE_UINT_64:
+      val = (int64_t) valp->numval;
+      break;
+    case TUNABLE_TYPE_SIZE_T:
+      val = (size_t) valp->numval;
+      break;
+    default:
+      __builtin_unreachable ();
     }
 
   bool unsigned_cmp = unsigned_tunable_type (cur->type.type_code);
 
-  val = valp->numval;
   min = minp != NULL ? *minp : cur->type.min;
   max = maxp != NULL ? *maxp : cur->type.max;
 
@@ -109,16 +120,24 @@ do_tunable_update_val (tunable_t *cur, const tunable_val_t *valp,
 
 /* Validate range of the input value and initialize the tunable CUR if it looks
    good.  */
-static void
+static bool
 tunable_initialize (tunable_t *cur, const char *strval, size_t len)
 {
   tunable_val_t val = { 0 };
 
   if (cur->type.type_code != TUNABLE_TYPE_STRING)
-    val.numval = (tunable_num_t) _dl_strtoul (strval, NULL);
+    {
+      char *endptr = NULL;
+      uint64_t numval = _dl_strtoul (strval, &endptr);
+      if (endptr != strval + len)
+	return false;
+      val.numval = (tunable_num_t) numval;
+    }
   else
     val.strval = (struct tunable_str_t) { strval, len };
   do_tunable_update_val (cur, &val, NULL, NULL);
+
+  return true;
 }
 
 bool
@@ -225,7 +244,13 @@ parse_tunables (const char *valstring)
     }
 
   for (int i = 0; i < ntunables; i++)
-    tunable_initialize (tunables[i].t, tunables[i].value, tunables[i].len);
+    if (!tunable_initialize (tunables[i].t, tunables[i].value,
+			     tunables[i].len))
+      _dl_error_printf ("WARNING: ld.so: invalid GLIBC_TUNABLES value `%.*s' "
+		       "for option `%s': ignored.\n",
+		       (int) tunables[i].len,
+		       tunables[i].value,
+		       tunables[i].t->name);
 }
 
 /* Initialize the tunables list from the environment.  For now we only use the
diff --git a/elf/tst-tunables.c b/elf/tst-tunables.c
index 188345b070..d6a1e1b3ac 100644
--- a/elf/tst-tunables.c
+++ b/elf/tst-tunables.c
@@ -53,6 +53,13 @@ static const struct test_t
     4096,
     0,
   },
+  {
+    "GLIBC_TUNABLES",
+    "glibc.malloc.mmap_threshold=-1",
+    0,
+    SIZE_MAX,
+    0,
+  },
   /* Empty tunable are ignored.  */
   {
     "GLIBC_TUNABLES",
@@ -224,6 +231,29 @@ static const struct test_t
     0,
     0,
   },
+  /* Invalid numbers are ignored.  */
+  {
+    "GLIBC_TUNABLES",
+    "glibc.malloc.check=abc:glibc.malloc.mmap_threshold=4096",
+    0,
+    4096,
+    0,
+  },
+  {
+    "GLIBC_TUNABLES",
+    "glibc.malloc.check=2:glibc.malloc.mmap_threshold=abc",
+    2,
+    0,
+    0,
+  },
+  {
+    "GLIBC_TUNABLES",
+    /* SIZE_MAX + 1 */
+    "glibc.malloc.mmap_threshold=18446744073709551616",
+    0,
+    0,
+    0,
+  },
   /* Also check some tunable aliases.  */
   {
     "MALLOC_CHECK_",
