[3.12] gh-132075: Fix possible use of sockaddr structures with uninitialized members (GH-132076) (GH-132087)

Now all structure members are initialized with zeroes by default.
(cherry picked from commit 345baa7)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Library/2025-04-04-16-22-03.gh-issue-132075.qMM5np.rst

@@ -0,0 +1,2 @@
+Fix possible use of :mod:`socket` address structures with uninitialized
+members. Now all structure members are initialized with zeroes by default.

Modules/socketmodule.c

@@ -1788,6 +1788,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
         assert(path.len >= 0);
 
         struct sockaddr_un* addr = &addrbuf->un;
+        memset(addr, 0, sizeof(struct sockaddr_un));
 #ifdef __linux__
         if (path.len == 0 || *(const char *)path.buf == 0) {
             /* Linux abstract namespace extension:
@@ -1831,6 +1832,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
     {
         int pid, groups;
         struct sockaddr_nl* addr = &addrbuf->nl;
+        memset(addr, 0, sizeof(struct sockaddr_nl));
         if (!PyTuple_Check(args)) {
             PyErr_Format(
                 PyExc_TypeError,
@@ -1858,6 +1860,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
     {
         unsigned int node, port;
         struct sockaddr_qrtr* addr = &addrbuf->sq;
+        memset(addr, 0, sizeof(struct sockaddr_qrtr));
         if (!PyTuple_Check(args)) {
             PyErr_Format(
                 PyExc_TypeError,
@@ -1935,6 +1938,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             return 0;
         }
         struct sockaddr_in* addr = &addrbuf->in;
+        memset(addr, 0, sizeof(struct sockaddr_in));
         result = setipaddr(s->state, host.buf, (struct sockaddr *)addr,
                            sizeof(*addr),  AF_INET);
         idna_cleanup(&host);
@@ -1980,6 +1984,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             return 0;
         }
         struct sockaddr_in6* addr = &addrbuf->in6;
+        memset(addr, 0, sizeof(struct sockaddr_in6));
         result = setipaddr(s->state, host.buf, (struct sockaddr *)addr,
                            sizeof(*addr), AF_INET6);
         idna_cleanup(&host);
@@ -2037,6 +2042,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
         {
             const char *straddr;
             struct sockaddr_rc *addr = &addrbuf->bt_rc;
+            memset(addr, 0, sizeof(struct sockaddr_rc));
             _BT_RC_MEMB(addr, family) = AF_BLUETOOTH;
 #ifdef MS_WINDOWS
             unsigned long channel;
@@ -2063,6 +2069,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
         case BTPROTO_HCI:
         {
             struct sockaddr_hci *addr = &addrbuf->bt_hci;
+            memset(addr, 0, sizeof(struct sockaddr_hci));
 #if defined(__NetBSD__) || defined(__DragonFly__)
             const char *straddr;
             _BT_HCI_MEMB(addr, family) = AF_BLUETOOTH;
@@ -2114,6 +2121,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             const char *straddr;
 
             struct sockaddr_sco *addr = &addrbuf->bt_sco;
+            memset(addr, 0, sizeof(struct sockaddr_sco));
             _BT_SCO_MEMB(addr, family) = AF_BLUETOOTH;
             if (!PyBytes_Check(args)) {
                 PyErr_Format(PyExc_OSError,
@@ -2191,6 +2199,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             return 0;
         }
         struct sockaddr_ll* addr = &addrbuf->ll;
+        memset(addr, 0, sizeof(struct sockaddr_ll));
         addr->sll_family = AF_PACKET;
         addr->sll_protocol = htons((short)protoNumber);
         addr->sll_ifindex = ifr.ifr_ifindex;
@@ -2275,6 +2284,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             struct ifreq ifr;
             Py_ssize_t len;
             struct sockaddr_can *addr = &addrbuf->can;
+            memset(addr, 0, sizeof(struct sockaddr_can));
 
             if (!PyTuple_Check(args)) {
                 PyErr_Format(PyExc_TypeError,
@@ -2327,6 +2337,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             unsigned long int rx_id, tx_id;
 
             struct sockaddr_can *addr = &addrbuf->can;
+            memset(addr, 0, sizeof(struct sockaddr_can));
 
             if (!PyArg_ParseTuple(args, "O&kk", PyUnicode_FSConverter,
                                               &interfaceName,
@@ -2374,6 +2385,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
             uint8_t j1939_addr;
 
             struct sockaddr_can *addr = &addrbuf->can;
+            memset(addr, 0, sizeof(struct sockaddr_can));
 
             if (!PyArg_ParseTuple(args, "O&KIB", PyUnicode_FSConverter,
                                               &interfaceName,
@@ -2426,6 +2438,7 @@ getsockaddrarg(PySocketSockObject *s, PyObject *args,
         case SYSPROTO_CONTROL:
         {
             struct sockaddr_ctl *addr = &addrbuf->ctl;
+            memset(addr, 0, sizeof(struct sockaddr_ctl));
             addr->sc_family = AF_SYSTEM;
             addr->ss_sysaddr = AF_SYS_CONTROL;