From 8bb544fbd2d6986a9b73d3fab49235a4baa96c23 Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bvanassche@acm.org>
Date: Sat, 31 Jul 2021 16:21:16 -0700
Subject: [PATCH] Linux: IF-MIB: Fix a memory leak

The Linux kernel regenerates proc files in their entirety every time a 4 KiB
boundary is crossed. This can result in reading the same network interface
twice if network information changes while it is being read. Fix a memory
leak that can be triggered if /proc/net/dev changes while being read.
---
 agent/mibgroup/if-mib/data_access/interface_linux.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/agent/mibgroup/if-mib/data_access/interface_linux.c b/agent/mibgroup/if-mib/data_access/interface_linux.c
index e99360a216..215b30e806 100644
--- a/agent/mibgroup/if-mib/data_access/interface_linux.c
+++ b/agent/mibgroup/if-mib/data_access/interface_linux.c
@@ -921,7 +921,15 @@ netsnmp_arch_interface_container_load(netsnmp_container* container,
         /*
          * add to container
          */
-        CONTAINER_INSERT(container, entry);
+        if (CONTAINER_INSERT(container, entry) != 0) {
+            netsnmp_interface_entry *existing =
+                CONTAINER_FIND(container, entry);
+            NETSNMP_LOGONCE((LOG_WARNING,
+                             "Encountered interface with index %" NETSNMP_PRIz "u twice: %s <> %s",
+                             entry->index, existing ? existing->name : "(?)",
+                             entry->name));
+            netsnmp_access_interface_entry_free(entry);
+        }
     }
 #ifdef NETSNMP_ENABLE_IPV6
     netsnmp_access_ipaddress_container_free(addr_container, 0);