Fix double-free on FreeBSD

src/libraries/Common/src/Interop/FreeBSD/Interop.Process.GetProcInfo.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 
 #pragma warning disable CA1823 // analyzer incorrectly flags fixed buffer length const (https://github.com/dotnet/roslyn/issues/37593)
@@ -186,11 +187,6 @@ public unsafe struct kinfo_proc
         public static unsafe kinfo_proc* GetProcInfo(int pid, bool threads, out int count)
         {
             Span<int> sysctlName = stackalloc int[4];
-            int bytesLength = 0;
-            byte* pBuffer = null;
-            kinfo_proc* kinfo = null;
-
-            count = -1;
 
             if (pid == 0)
             {
@@ -207,23 +203,17 @@ public unsafe struct kinfo_proc
             sysctlName[1] = KERN_PROC;
             sysctlName[0] = CTL_KERN;
 
-            try
-            {
-                Interop.Sys.Sysctl(sysctlName, ref pBuffer, ref bytesLength);
-                kinfo = (kinfo_proc*)pBuffer;
-                if (kinfo->ki_structsize != sizeof(kinfo_proc))
-                {
-                    // failed consistency check
-                    throw new ArgumentOutOfRangeException(nameof(pid));
-                }
-
-                count = (int)bytesLength / sizeof(kinfo_proc);
-            }
-            finally
-            {
-                Marshal.FreeHGlobal((IntPtr)pBuffer);
-            }
+            byte* pBuffer = null;
+            int bytesLength = 0;
+            Interop.Sys.Sysctl(sysctlName, ref pBuffer, ref bytesLength);
+
+            kinfo_proc* kinfo = (kinfo_proc*)pBuffer;
+
+            Debug.Assert(kinfo->ki_structsize == sizeof(kinfo_proc));
+
+            count = (int)bytesLength / sizeof(kinfo_proc);
 
+            // Buffer ownership transferred to the caller
             return kinfo;
         }
     }

src/libraries/Common/src/Interop/FreeBSD/Interop.Process.cs

@@ -65,7 +65,7 @@ internal static unsafe int[] ListAllPids()
             }
             finally
             {
-                Marshal.FreeHGlobal((IntPtr)entries);
+                NativeMemory.Free(entries);
             }
         }
 
@@ -87,7 +87,7 @@ internal static unsafe int[] ListAllPids()
             }
             finally
             {
-                Marshal.FreeHGlobal((IntPtr)pBuffer);
+                NativeMemory.Free(pBuffer);
             }
         }
 
@@ -107,9 +107,9 @@ public static unsafe ProcessInfo GetProcessInfoById(int pid)
                 throw new ArgumentOutOfRangeException(nameof(pid));
             }
 
-            kinfo_proc* kinfo = GetProcInfo(pid, true, out int count);
             ProcessInfo info;
 
+            kinfo_proc* kinfo = GetProcInfo(pid, true, out int count);
             try
             {
                 if (count < 1)
@@ -142,7 +142,7 @@ public static unsafe ProcessInfo GetProcessInfoById(int pid)
             }
             finally
             {
-                Marshal.FreeHGlobal((IntPtr)kinfo);
+                NativeMemory.Free(kinfo);
             }
 
             return info;
@@ -160,12 +160,11 @@ public static unsafe ProcessInfo GetProcessInfoById(int pid)
         public static unsafe proc_stats GetThreadInfo(int pid, int tid)
         {
             proc_stats ret = default;
-            kinfo_proc* info = null;
             int count;
 
+            kinfo_proc* info = GetProcInfo(pid, (tid != 0), out count);
             try
             {
-                info = GetProcInfo(pid, (tid != 0), out count);
                 if (info != null && count >= 1)
                 {
                     if (tid == 0)
@@ -194,7 +193,7 @@ public static unsafe proc_stats GetThreadInfo(int pid, int tid)
             }
             finally
             {
-                Marshal.FreeHGlobal((IntPtr)info);
+                NativeMemory.Free(info);
             }
 
             return ret;

src/libraries/System.Private.CoreLib/src/System/Environment.FreeBSD.cs

@@ -7,6 +7,20 @@ namespace System
 {
     public static partial class Environment
     {
-        public static unsafe long WorkingSet => Interop.Process.GetProcInfo(ProcessId, true, out _)->ki_rssize;
+        public static unsafe long WorkingSet
+        {
+            get
+            {
+                Interop.Process.kinfo_proc* processInfo = Interop.Process.GetProcInfo(ProcessId, true, out _);
+                try
+                {
+                    return processInfo->ki_rssize;
+                }
+                finally
+                {
+                    NativeMemory.Free(processInfo);
+                }
+            }
+        }
     }
 }