Remove the memory leak

src/libraries/Common/src/Interop/Unix/System.Native/Interop.GetEnviron.cs

@@ -10,5 +10,8 @@ internal unsafe partial class Sys
     {
         [DllImport(Interop.Libraries.SystemNative, EntryPoint = "SystemNative_GetEnviron")]
         internal static extern unsafe IntPtr GetEnviron();
+
+        [DllImport(Interop.Libraries.SystemNative, EntryPoint = "SystemNative_FreeEnviron")]
+        internal static extern unsafe void FreeEnviron(IntPtr environ);
     }
 }

src/libraries/Native/Unix/System.Native/entrypoints.c

@@ -261,6 +261,7 @@ static const Entry s_sysNative[] =
     DllImportEntry(SystemNative_GetGroups)
     DllImportEntry(SystemNative_GetEnv)
     DllImportEntry(SystemNative_GetEnviron)
+    DllImportEntry(SystemNative_FreeEnviron)
 };
 
 EXTERN_C const void* SystemResolveDllImport(const char* name);

src/libraries/Native/Unix/System.Native/pal_environment.c

@@ -24,3 +24,8 @@ char** SystemNative_GetEnviron()
     return environ;
 #endif
 }
+
+void SystemNative_FreeEnviron(char** environ)
+{
+    // no op
+}

src/libraries/Native/Unix/System.Native/pal_environment.h

@@ -8,4 +8,6 @@
 
 PALEXPORT char* SystemNative_GetEnv(const char* variable);
 
-PALEXPORT char** SystemNative_GetEnviron(void);
+PALEXPORT char** SystemNative_GetEnviron(int32_t *releaseMemory);
+
+PALEXPORT void SystemNative_FreeEnviron(char** environ);

src/libraries/Native/Unix/System.Native/pal_environment.m

@@ -14,6 +14,8 @@
     return getenv(variable);
 }
 
+static char *empty_key_value_pair = "=";
+
 static void get_environ_helper(const void *key, const void *value, void *context)
 {
     char ***temp_environ_ptr = (char***)context;
@@ -30,35 +32,47 @@ static void get_environ_helper(const void *key, const void *value, void *context
         key_value_pair[utf8_key_length] = '=';
         strcpy(key_value_pair + utf8_key_length + 1, utf8_value);
     }
+    else
+    {
+        // In case of failed allocation add pointer to preallocated entry. This is
+        // ignored on the managed side and skipped over in SystemNative_FreeEnviron.
+        key_value_pair = empty_key_value_pair;
+    }
 
     **temp_environ_ptr = key_value_pair;
     (*temp_environ_ptr)++;
 }
 
 char** SystemNative_GetEnviron()
 {
-    static char **environ;
+    char **temp_environ;
+    char **temp_environ_ptr;
 
-    // NOTE: This function is not thread-safe and it leaks one array per process. This is
-    // intentional behavior and the managed code is expected to take additional guards
-    // around this call.
-    if (environ == NULL)
+    CFDictionaryRef environment = (CFDictionaryRef)[[NSProcessInfo processInfo] environment];
+    int count = CFDictionaryGetCount(environment);
+    temp_environ = (char **)malloc((count + 1) * sizeof(char *));
+    if (temp_environ != NULL)
     {
-        int environ_size = 1;
-        char **temp_environ;
-        char **temp_environ_ptr;
+        temp_environ_ptr = temp_environ;
+        CFDictionaryApplyFunction(environment, get_environ_helper, &temp_environ_ptr);
+        *temp_environ_ptr = NULL;
+    }
+
+    return temp_environ;
+}
 
-        CFDictionaryRef environment = (CFDictionaryRef)[[NSProcessInfo processInfo] environment];
-        int count = CFDictionaryGetCount(environment);
-        temp_environ = (char **)malloc((count + 1) * sizeof(char *));
-        if (temp_environ != NULL)
+void SystemNative_FreeEnviron(char** environ)
+{
+    if (environ != NULL)
+    {
+        for (char** environ_ptr = environ; *environ_ptr != NULL; environ_ptr++)
         {
-            temp_environ_ptr = temp_environ;
-            CFDictionaryApplyFunction(environment, get_environ_helper, &temp_environ_ptr);
-            *temp_environ_ptr = NULL;
-            environ = temp_environ;
+            if (*environ_ptr != empty_key_value_pair)
+            {
+                free(*environ_ptr);
+            }
         }
-    }
 
-    return environ;
-}
+        free(environ);
+    }
+}

src/mono/System.Private.CoreLib/src/System/Environment.Unix.Mono.cs

@@ -92,16 +92,20 @@ private static Dictionary<string, string> GetSystemEnvironmentVariables()
             IntPtr block = Interop.Sys.GetEnviron();
             if (block != IntPtr.Zero)
             {
+                IntPtr blockIterator = block;
+
                 // Per man page, environment variables come back as an array of pointers to strings
                 // Parse each pointer of strings individually
-                while (ParseEntry(block, out string? key, out string? value))
+                while (ParseEntry(blockIterator, out string? key, out string? value))
                 {
                     if (key != null && value != null)
                         results.Add(key, value);
 
                     // Increment to next environment variable entry
-                    block += IntPtr.Size;
+                    blockIterator += IntPtr.Size;
                 }
+
+                Interop.Sys.FreeEnviron(block);
             }
 
             return results;