diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index a5aaf9b7252..91d324dcd3e 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -3,6 +3,7 @@
 import unittest
 import sys
 import os
+import _testcapi
 from test import support
 
 # Skip this test if the _tkinter module wasn't built.
@@ -236,8 +237,21 @@ class TclTest(unittest.TestCase):
             self.assertEqual(split(arg), res, msg=arg)
 
 
+class BigmemTclTest(unittest.TestCase):
+
+    def setUp(self):
+        self.interp = Tcl()
+
+    @unittest.skipUnless(_testcapi.INT_MAX < _testcapi.PY_SSIZE_T_MAX,
+                         "needs UINT_MAX < SIZE_MAX")
+    @support.bigmemtest(size=_testcapi.INT_MAX + 1, memuse=5, dry_run=False)
+    def test_huge_string(self, size):
+        value = ' ' * size
+        self.assertRaises(OverflowError, self.interp.call, 'set', '_', value)
+
+
 def test_main():
-    support.run_unittest(TclTest, TkinterTest)
+    support.run_unittest(TclTest, TkinterTest, BigmemTclTest)
 
 if __name__ == "__main__":
     test_main()
diff --git a/Misc/NEWS b/Misc/NEWS
index b95ce2d8d2c..602d27ff546 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -38,6 +38,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #17119: Fixed integer overflows when processing large strings and tuples
+  in the tkinter module.
+
 - Issue #18747: Re-seed OpenSSL's pseudo-random number generator after fork.
   A pthread_atfork() child handler is used to seeded the PRNG with pid, time
   and some stack data.
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 637a9bb205d..c6f63ac8882 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -47,6 +47,9 @@ Copyright (C) 1994 Steen Lumholt.
 #define PyBool_FromLong       PyLong_FromLong
 #endif
 
+#define CHECK_SIZE(size, elemsize) \
+    ((size_t)(size) <= Py_MAX((size_t)INT_MAX, UINT_MAX / (size_t)(elemsize)))
+
 /* Starting with Tcl 8.4, many APIs offer const-correctness.  Unfortunately,
    making _tkinter correct for this API means to break earlier
    versions. USE_COMPAT_CONST allows to make _tkinter work with both 8.4 and
@@ -850,12 +853,18 @@ AsObj(PyObject *value)
     else if (PyFloat_Check(value))
         return Tcl_NewDoubleObj(PyFloat_AS_DOUBLE(value));
     else if (PyTuple_Check(value)) {
-        Tcl_Obj **argv = (Tcl_Obj**)
-            ckalloc(PyTuple_Size(value)*sizeof(Tcl_Obj*));
-        int i;
+        Tcl_Obj **argv;
+        Py_ssize_t size, i;
+
+        size = PyTuple_Size(value);
+        if (!CHECK_SIZE(size, sizeof(Tcl_Obj *))) {
+            PyErr_SetString(PyExc_OverflowError, "tuple is too long");
+            return NULL;
+        }
+        argv = (Tcl_Obj **) ckalloc(((size_t)size) * sizeof(Tcl_Obj *));
         if(!argv)
           return 0;
-        for(i=0;i<PyTuple_Size(value);i++)
+        for (i = 0; i < size; i++)
           argv[i] = AsObj(PyTuple_GetItem(value,i));
         result = Tcl_NewListObj(PyTuple_Size(value), argv);
         ckfree(FREECAST argv);
@@ -874,6 +883,10 @@ AsObj(PyObject *value)
 
         inbuf = PyUnicode_DATA(value);
         size = PyUnicode_GET_LENGTH(value);
+        if (!CHECK_SIZE(size, sizeof(Tcl_UniChar))) {
+            PyErr_SetString(PyExc_OverflowError, "string is too long");
+            return NULL;
+        }
         kind = PyUnicode_KIND(value);
         allocsize = ((size_t)size) * sizeof(Tcl_UniChar);
         outbuf = (Tcl_UniChar*)ckalloc(allocsize);
@@ -1029,7 +1042,7 @@ static Tcl_Obj**
 Tkapp_CallArgs(PyObject *args, Tcl_Obj** objStore, int *pobjc)
 {
     Tcl_Obj **objv = objStore;
-    int objc = 0, i;
+    Py_ssize_t objc = 0, i;
     if (args == NULL)
         /* do nothing */;
 
@@ -1044,7 +1057,11 @@ Tkapp_CallArgs(PyObject *args, Tcl_Obj** objStore, int *pobjc)
         objc = PyTuple_Size(args);
 
         if (objc > ARGSZ) {
-            objv = (Tcl_Obj **)ckalloc(objc * sizeof(char *));
+            if (!CHECK_SIZE(objc, sizeof(Tcl_Obj *))) {
+                PyErr_SetString(PyExc_OverflowError, "tuple is too long");
+                return NULL;
+            }
+            objv = (Tcl_Obj **)ckalloc(((size_t)objc) * sizeof(Tcl_Obj *));
             if (objv == NULL) {
                 PyErr_NoMemory();
                 objc = 0;