Fix GetFactoryMacAddress memory leak.

Previously this allocated memory and never freed it. The size is known
at compile time, so we just allocate memory on the stack which
simplifies error handling.

Also documents behavior on error.

Bug: 132705022
Test: m -j32 vts && vts-tradefed run vts-hal --skip-preconditions --module VtsHalWifiV1_3Target
Change-Id: I9d806d4212d6c702717915bf25c2cde3831cd297

1 files changed, 6 insertions, 8 deletions

diff --git a/libwifi_system_iface/interface_tool.cpp b/libwifi_system_iface/interface_tool.cpp
index 261698215..17895d6ef 100644
--- a/libwifi_system_iface/interface_tool.cpp
+++ b/libwifi_system_iface/interface_tool.cpp
@@ -138,7 +138,12 @@ bool InterfaceTool::SetMacAddress(const char* if_name,
 std::array<uint8_t, ETH_ALEN> InterfaceTool::GetFactoryMacAddress(const char* if_name) {
   std::array<uint8_t, ETH_ALEN> paddr = {};
   struct ifreq ifr;
-  struct ethtool_perm_addr *epaddr;
+  struct {
+    // Allocate ETH_ALEN bytes after ethtool_perm_addr.
+    struct ethtool_perm_addr epaddr;
+    uint8_t data[ETH_ALEN];
+  } epaddr_buf;
+  struct ethtool_perm_addr* epaddr = &epaddr_buf.epaddr;
 
   base::unique_fd sock(socket(PF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0));
   if (sock.get() < 0) {
@@ -151,13 +156,6 @@ std::array<uint8_t, ETH_ALEN> InterfaceTool::GetFactoryMacAddress(const char* if
     return paddr;  // logging done internally
   }
 
-  epaddr = (ethtool_perm_addr*) malloc(sizeof(struct ethtool_perm_addr) + ETH_ALEN);
-  if (!epaddr) {
-    LOG(ERROR) << "Failed to set memory for mac address ("
-               << strerror(errno) << ")";
-    return paddr;
-  }
-
   epaddr->cmd = ETHTOOL_GPERMADDR;
   epaddr->size = ETH_ALEN;
   ifr.ifr_data = epaddr;