diff --git a/cephfs/command.go b/cephfs/command.go
index 3ef780cbb..e12e5d7bd 100644
--- a/cephfs/command.go
+++ b/cephfs/command.go
@@ -14,6 +14,10 @@ import (
 	"github.com/ceph/go-ceph/internal/cutil"
 )
 
+func cephBufferFree(p unsafe.Pointer) {
+	C.ceph_buffer_free((*C.char)(p))
+}
+
 // MdsCommand sends commands to the specified MDS.
 func (mount *MountInfo) MdsCommand(mdsSpec string, args [][]byte) ([]byte, string, error) {
 	return mount.mdsCommand(mdsSpec, args, nil)
@@ -40,7 +44,7 @@ func (mount *MountInfo) mdsCommand(mdsSpec string, args [][]byte, inputBuffer []
 	defer C.free(unsafe.Pointer(spec))
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput(cephBufferFree)
 	defer co.Free()
 
 	ret := C.ceph_mds_command(
diff --git a/internal/cutil/command_output.go b/internal/cutil/command_output.go
index b6863a73f..4855c5813 100644
--- a/internal/cutil/command_output.go
+++ b/internal/cutil/command_output.go
@@ -12,6 +12,7 @@ import (
 // CommandOutput can be used to manage the outputs of ceph's *_command
 // functions.
 type CommandOutput struct {
+	free      FreeFunc
 	outBuf    *C.char
 	outBufLen C.size_t
 	outs      *C.char
@@ -21,17 +22,19 @@ type CommandOutput struct {
 // NewCommandOutput returns an empty CommandOutput. The pointers that
 // a CommandOutput provides can be used to get the results of ceph's
 // *_command functions.
-func NewCommandOutput() *CommandOutput {
-	return &CommandOutput{}
+func NewCommandOutput(free FreeFunc) *CommandOutput {
+	return &CommandOutput{
+		free: free,
+	}
 }
 
 // Free any C memory tracked by this object.
 func (co *CommandOutput) Free() {
 	if co.outBuf != nil {
-		C.free(unsafe.Pointer(co.outBuf))
+		co.free(unsafe.Pointer(co.outBuf))
 	}
 	if co.outs != nil {
-		C.free(unsafe.Pointer(co.outs))
+		co.free(unsafe.Pointer(co.outs))
 	}
 }
 
@@ -79,3 +82,9 @@ func testSetString(strp CharPtrPtr, lenp SizeTPtr, s string) {
 	*sp = C.CString(s)
 	*lp = C.size_t(len(s))
 }
+
+// free wraps C.free.
+// Required for unit tests that may not use cgo directly.
+func free(p unsafe.Pointer) {
+	C.free(p)
+}
diff --git a/internal/cutil/command_output_test.go b/internal/cutil/command_output_test.go
index 41619a6fe..3b321a812 100644
--- a/internal/cutil/command_output_test.go
+++ b/internal/cutil/command_output_test.go
@@ -8,12 +8,12 @@ import (
 
 func TestCommandOutput(t *testing.T) {
 	t.Run("newAndFree", func(t *testing.T) {
-		co := NewCommandOutput()
+		co := NewCommandOutput(free)
 		assert.NotNil(t, co)
 		co.Free()
 	})
 	t.Run("setValues", func(t *testing.T) {
-		co := NewCommandOutput()
+		co := NewCommandOutput(free)
 		assert.NotNil(t, co)
 		defer co.Free()
 		testSetString(co.OutBuf(), co.OutBufLen(), "i got style")
@@ -23,7 +23,7 @@ func TestCommandOutput(t *testing.T) {
 		assert.EqualValues(t, "i got rhythm", s)
 	})
 	t.Run("setOnlyOutBuf", func(t *testing.T) {
-		co := NewCommandOutput()
+		co := NewCommandOutput(free)
 		assert.NotNil(t, co)
 		defer co.Free()
 		testSetString(co.OutBuf(), co.OutBufLen(), "i got style")
@@ -32,7 +32,7 @@ func TestCommandOutput(t *testing.T) {
 		assert.EqualValues(t, "", s)
 	})
 	t.Run("setOnlyOuts", func(t *testing.T) {
-		co := NewCommandOutput()
+		co := NewCommandOutput(free)
 		assert.NotNil(t, co)
 		defer co.Free()
 		testSetString(co.Outs(), co.OutsLen(), "i got rhythm")
diff --git a/internal/cutil/type_aliases.go b/internal/cutil/type_aliases.go
index f566fdaec..79495ef98 100644
--- a/internal/cutil/type_aliases.go
+++ b/internal/cutil/type_aliases.go
@@ -23,3 +23,6 @@ type CharPtr unsafe.Pointer
 
 // SizeTPtr is an unsafe pointer wrapping C's `size_t*`.
 type SizeTPtr unsafe.Pointer
+
+// FreeFunc is a wrapper around calls to, or act like, C's free function.
+type FreeFunc func(unsafe.Pointer)
diff --git a/rados/command.go b/rados/command.go
index 1d6a1b565..2601bfddd 100644
--- a/rados/command.go
+++ b/rados/command.go
@@ -11,6 +11,10 @@ import (
 	"github.com/ceph/go-ceph/internal/cutil"
 )
 
+func radosBufferFree(p unsafe.Pointer) {
+	C.rados_buffer_free((*C.char)(p))
+}
+
 // MonCommand sends a command to one of the monitors
 func (c *Conn) MonCommand(args []byte) ([]byte, string, error) {
 	return c.monCommand(args, nil)
@@ -24,7 +28,7 @@ func (c *Conn) MonCommandWithInputBuffer(args, inputBuffer []byte) ([]byte, stri
 func (c *Conn) monCommand(args, inputBuffer []byte) ([]byte, string, error) {
 	ci := cutil.NewCommandInput([][]byte{args}, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_mon_command(
@@ -70,7 +74,7 @@ func (c *Conn) pgCommand(pgid []byte, args [][]byte, inputBuffer []byte) ([]byte
 	defer C.free(unsafe.Pointer(name))
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_pg_command(
@@ -107,7 +111,7 @@ func (c *Conn) MgrCommandWithInputBuffer(args [][]byte, inputBuffer []byte) ([]b
 func (c *Conn) mgrCommand(args [][]byte, inputBuffer []byte) ([]byte, string, error) {
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_mgr_command(