From 92619c833e680d63a190d5e874027126ef21d121 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>
(cherry picked from commit 334c4b8bdcb82597a8346489291defbaf254a159)
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 d52362d5f6..fc5d61c2e3 100644
--- a/src/runtime/pkg/govmm/qemu/qemu.go
+++ b/src/runtime/pkg/govmm/qemu/qemu.go
@@ -2611,9 +2611,6 @@ type Config struct {
 	// PidFile is the -pidfile parameter
 	PidFile string
 
-	// LogFile is the -D parameter
-	LogFile string
-
 	qemuParams []string
 }
 
@@ -2941,13 +2938,6 @@ 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{}
@@ -2986,7 +2976,6 @@ 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 563a9f7fb1..efa7dc557f 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 8b0b7cb971..c2f8de743c 100644
--- a/src/runtime/virtcontainers/qemu.go
+++ b/src/runtime/virtcontainers/qemu.go
@@ -902,10 +902,6 @@ 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 {
@@ -1069,19 +1065,6 @@ func (q *qemu) StopVM(ctx context.Context, waitOnly bool) error {
 		q.stopped = true
 	}()
 
-	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
 	}