bpo-30061: Check if PyObject_Size()/PySequence_Size()/PyMapping_Size() (#1096) (#1180)

raised an error.

(cherry picked from commit bf623ae8843dc30b28c574bec8d29fc14be59d86)
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 2ea5e2d..f4bbc89 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -6650,7 +6650,7 @@
 os_setgroups(PyObject *module, PyObject *groups)
 /*[clinic end generated code: output=3fcb32aad58c5ecd input=fa742ca3daf85a7e]*/
 {
-    int i, len;
+    Py_ssize_t i, len;
     gid_t grouplist[MAX_GROUPS];
 
     if (!PySequence_Check(groups)) {
@@ -6658,6 +6658,9 @@
         return NULL;
     }
     len = PySequence_Size(groups);
+    if (len < 0) {
+        return NULL;
+    }
     if (len > MAX_GROUPS) {
         PyErr_SetString(PyExc_ValueError, "too many groups");
         return NULL;
@@ -7886,9 +7889,9 @@
 #if (defined(HAVE_SENDFILE) && (defined(__FreeBSD__) || defined(__DragonFly__) \
     || defined(__APPLE__))) || defined(HAVE_READV) || defined(HAVE_WRITEV)
 static Py_ssize_t
-iov_setup(struct iovec **iov, Py_buffer **buf, PyObject *seq, int cnt, int type)
+iov_setup(struct iovec **iov, Py_buffer **buf, PyObject *seq, Py_ssize_t cnt, int type)
 {
-    int i, j;
+    Py_ssize_t i, j;
     Py_ssize_t blen, total = 0;
 
     *iov = PyMem_New(struct iovec, cnt);
@@ -7965,8 +7968,7 @@
 os_readv_impl(PyObject *module, int fd, PyObject *buffers)
 /*[clinic end generated code: output=792da062d3fcebdb input=e679eb5dbfa0357d]*/
 {
-    int cnt;
-    Py_ssize_t n;
+    Py_ssize_t cnt, n;
     int async_err = 0;
     struct iovec *iov;
     Py_buffer *buf;
@@ -7978,6 +7980,8 @@
     }
 
     cnt = PySequence_Size(buffers);
+    if (cnt < 0)
+        return -1;
 
     if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
         return -1;
@@ -8116,15 +8120,24 @@
                 "sendfile() headers must be a sequence");
             return NULL;
         } else {
-            Py_ssize_t i = 0; /* Avoid uninitialized warning */
-            sf.hdr_cnt = PySequence_Size(headers);
-            if (sf.hdr_cnt > 0 &&
-                (i = iov_setup(&(sf.headers), &hbuf,
-                                headers, sf.hdr_cnt, PyBUF_SIMPLE)) < 0)
+            Py_ssize_t i = PySequence_Size(headers);
+            if (i < 0)
                 return NULL;
+            if (i > INT_MAX) {
+                PyErr_SetString(PyExc_OverflowError,
+                    "sendfile() header is too large");
+                return NULL;
+            }
+            if (i > 0) {
+                sf.hdr_cnt = (int)i;
+                i = iov_setup(&(sf.headers), &hbuf,
+                              headers, sf.hdr_cnt, PyBUF_SIMPLE);
+                if (i < 0)
+                    return NULL;
 #ifdef __APPLE__
-            sbytes += i;
+                sbytes += i;
 #endif
+            }
         }
     }
     if (trailers != NULL) {
@@ -8133,15 +8146,24 @@
                 "sendfile() trailers must be a sequence");
             return NULL;
         } else {
-            Py_ssize_t i = 0; /* Avoid uninitialized warning */
-            sf.trl_cnt = PySequence_Size(trailers);
-            if (sf.trl_cnt > 0 &&
-                (i = iov_setup(&(sf.trailers), &tbuf,
-                                trailers, sf.trl_cnt, PyBUF_SIMPLE)) < 0)
+            Py_ssize_t i = PySequence_Size(trailers);
+            if (i < 0)
                 return NULL;
+            if (i > INT_MAX) {
+                PyErr_SetString(PyExc_OverflowError,
+                    "sendfile() trailer is too large");
+                return NULL;
+            }
+            if (i > 0) {
+                sf.trl_cnt = (int)i;
+                i = iov_setup(&(sf.trailers), &tbuf,
+                              trailers, sf.trl_cnt, PyBUF_SIMPLE);
+                if (i < 0)
+                    return NULL;
 #ifdef __APPLE__
-            sbytes += i;
+                sbytes += i;
 #endif
+            }
         }
     }
 
@@ -8411,7 +8433,7 @@
 os_writev_impl(PyObject *module, int fd, PyObject *buffers)
 /*[clinic end generated code: output=56565cfac3aac15b input=5b8d17fe4189d2fe]*/
 {
-    int cnt;
+    Py_ssize_t cnt;
     Py_ssize_t result;
     int async_err = 0;
     struct iovec *iov;
@@ -8423,6 +8445,8 @@
         return -1;
     }
     cnt = PySequence_Size(buffers);
+    if (cnt < 0)
+        return -1;
 
     if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0) {
         return -1;