From 334c4b8bdcb82597a8346489291defbaf254a159 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Thu, 15 Dec 2022 09:14:14 +0100
Subject: [PATCH] runtime: Drop QEMU log file support

The QEMU log file is essentially about fine grain tracing of QEMU
internals and mostly useful for developpers, not production. Notably,
the log file isn't limited in size, nor rotated in any way. It means
that a container running in the VM could possibly flood the log file
with a guest triggerable trace. For example, on openshift, the log
file is supposed to reside on a per-VM 14 GiB tmpfs mount. This means
that each pod running with the kata runtime could potentially consume
this amount of host RAM which is not acceptable.

Error messages are best collected from QEMU's stderr as kata is doing
now since PR #5736 was merged. Drop support for the QEMU log file
because it doesn't bring any value but can certainly do harm.

Fixes #6173

Signed-off-by: Greg Kurz <groug@kaod.org>
---
 src/runtime/pkg/govmm/qemu/qemu.go      | 11 -----------
 src/runtime/pkg/govmm/qemu/qemu_test.go |  5 +----
 src/runtime/virtcontainers/qemu.go      | 17 -----------------
 3 files changed, 1 insertion(+), 32 deletions(-)

diff --git a/src/runtime/pkg/govmm/qemu/qemu.go b/src/runtime/pkg/govmm/qemu/qemu.go
index 148212f511..6932826d7d 100644
--- a/src/runtime/pkg/govmm/qemu/qemu.go
+++ b/src/runtime/pkg/govmm/qemu/qemu.go
@@ -2628,9 +2628,6 @@ type Config struct {
 	// PidFile is the -pidfile parameter
 	PidFile string
 
-	// LogFile is the -D parameter
-	LogFile string
-
 	qemuParams []string
 }
 
@@ -2968,13 +2965,6 @@ func (config *Config) appendPidFile() {
 	}
 }
 
-func (config *Config) appendLogFile() {
-	if config.LogFile != "" {
-		config.qemuParams = append(config.qemuParams, "-D")
-		config.qemuParams = append(config.qemuParams, config.LogFile)
-	}
-}
-
 func (config *Config) appendFwCfg(logger QMPLog) {
 	if logger == nil {
 		logger = qmpNullLogger{}
@@ -3013,7 +3003,6 @@ func LaunchQemu(config Config, logger QMPLog) (*exec.Cmd, io.ReadCloser, error)
 	config.appendIOThreads()
 	config.appendIncoming()
 	config.appendPidFile()
-	config.appendLogFile()
 	config.appendFwCfg(logger)
 	config.appendSeccompSandbox()
 
diff --git a/src/runtime/pkg/govmm/qemu/qemu_test.go b/src/runtime/pkg/govmm/qemu/qemu_test.go
index b7428d1019..34ca776dfc 100644
--- a/src/runtime/pkg/govmm/qemu/qemu_test.go
+++ b/src/runtime/pkg/govmm/qemu/qemu_test.go
@@ -764,8 +764,7 @@ func TestAppendQMPSocketServer(t *testing.T) {
 }
 
 var pidfile = "/run/vc/vm/iamsandboxid/pidfile"
-var logfile = "/run/vc/vm/iamsandboxid/logfile"
-var qemuString = "-name cc-qemu -cpu host -uuid " + agentUUID + " -pidfile " + pidfile + " -D " + logfile
+var qemuString = "-name cc-qemu -cpu host -uuid " + agentUUID + " -pidfile " + pidfile
 
 func TestAppendStrings(t *testing.T) {
 	config := Config{
@@ -774,14 +773,12 @@ func TestAppendStrings(t *testing.T) {
 		UUID:     agentUUID,
 		CPUModel: "host",
 		PidFile:  pidfile,
-		LogFile:  logfile,
 	}
 
 	config.appendName()
 	config.appendCPUModel()
 	config.appendUUID()
 	config.appendPidFile()
-	config.appendLogFile()
 
 	result := strings.Join(config.qemuParams, " ")
 	if result != qemuString {
diff --git a/src/runtime/virtcontainers/qemu.go b/src/runtime/virtcontainers/qemu.go
index d59d67d801..3e1fd4bfda 100644
--- a/src/runtime/virtcontainers/qemu.go
+++ b/src/runtime/virtcontainers/qemu.go
@@ -940,10 +940,6 @@ func (q *qemu) StartVM(ctx context.Context, timeout int) error {
 		return err
 	}
 	q.Logger().WithField("vm path", vmPath).Info("created vm path")
-	// append logfile only on debug
-	if q.config.Debug {
-		q.qemuConfig.LogFile = filepath.Join(vmPath, "qemu.log")
-	}
 
 	defer func() {
 		if err != nil {
@@ -1108,19 +1104,6 @@ func (q *qemu) StopVM(ctx context.Context, waitOnly bool) (err error) {
 		}
 	}()
 
-	if q.config.Debug && q.qemuConfig.LogFile != "" {
-		f, err := os.OpenFile(q.qemuConfig.LogFile, os.O_RDONLY, 0)
-		if err == nil {
-			scanner := bufio.NewScanner(f)
-			for scanner.Scan() {
-				q.Logger().WithField("file", q.qemuConfig.LogFile).Debug(scanner.Text())
-			}
-			if err := scanner.Err(); err != nil {
-				q.Logger().WithError(err).Debug("read qemu log failed")
-			}
-		}
-	}
-
 	if err := q.qmpSetup(); err != nil {
 		return err
 	}