Ensure memcpy of mac lengths does not overflow buffers (#18757)

* Ensure memcpy of mac lengths does not overflow buffers

* Ensure 0 memset in case mac address is too short

* Use std::min instead of explicit if

* Add missing include and cast for std::min

src/platform/Linux/ConfigurationManagerImpl.cpp

@@ -37,6 +37,8 @@
 #include <platform/Linux/PosixConfig.h>
 #include <platform/internal/GenericConfigurationManagerImpl.ipp>
 
+#include <algorithm>
+
 namespace chip {
 namespace DeviceLayer {
 
@@ -130,13 +132,18 @@ CHIP_ERROR ConfigurationManagerImpl::GetPrimaryWiFiMACAddress(uint8_t * buf)
     CHIP_ERROR error           = CHIP_NO_ERROR;
     bool found                 = false;
 
+    // TODO: ideally the buffer size should have been passed as a span, however
+    //       for now use the size that is validated in GenericConfigurationManagerImpl.ipp
+    constexpr size_t kExpectedBufMinSize = ConfigurationManager::kPrimaryMACAddressLength;
+    memset(buf, 0, kExpectedBufMinSize);
+
     VerifyOrExit(getifaddrs(&addresses) == 0, error = CHIP_ERROR_INTERNAL);
     for (auto addr = addresses; addr != nullptr; addr = addr->ifa_next)
     {
         if ((addr->ifa_addr) && (addr->ifa_addr->sa_family == AF_PACKET) && strncmp(addr->ifa_name, "lo", IFNAMSIZ) != 0)
         {
             struct sockaddr_ll * mac = (struct sockaddr_ll *) addr->ifa_addr;
-            memcpy(buf, mac->sll_addr, mac->sll_halen);
+            memcpy(buf, mac->sll_addr, std::min<size_t>(mac->sll_halen, kExpectedBufMinSize));
             found = true;
             break;
         }