5 files changed, 40 insertions, 18 deletions

diff --git a/pkg/sentry/arch/arch_arm64.go b/pkg/sentry/arch/arch_arm64.go
index 372b650b9..885115ae2 100644
--- a/pkg/sentry/arch/arch_arm64.go
+++ b/pkg/sentry/arch/arch_arm64.go
@@ -53,6 +53,11 @@ const (
 	preferredPIELoadAddr usermem.Addr = maxAddr64 / 6 * 5
 )
 
+var (
+	// CPUIDInstruction doesn't exist on ARM64.
+	CPUIDInstruction = []byte{}
+)
+
 // These constants are selected as heuristics to help make the Platform's
 // potentially limited address space conform as closely to Linux as possible.
 const (
diff --git a/pkg/sentry/fs/fsutil/inode.go b/pkg/sentry/fs/fsutil/inode.go
index daecc4ffe..1922ff08c 100644
--- a/pkg/sentry/fs/fsutil/inode.go
+++ b/pkg/sentry/fs/fsutil/inode.go
@@ -259,8 +259,8 @@ func (i *InodeSimpleExtendedAttributes) ListXattr(context.Context, *fs.Inode, ui
 
 // RemoveXattr implements fs.InodeOperations.RemoveXattr.
 func (i *InodeSimpleExtendedAttributes) RemoveXattr(_ context.Context, _ *fs.Inode, name string) error {
-	i.mu.RLock()
-	defer i.mu.RUnlock()
+	i.mu.Lock()
+	defer i.mu.Unlock()
 	if _, ok := i.xattrs[name]; ok {
 		delete(i.xattrs, name)
 		return nil
diff --git a/pkg/sentry/kernel/task_run.go b/pkg/sentry/kernel/task_run.go
index 5568c91bc..799cbcd93 100644
--- a/pkg/sentry/kernel/task_run.go
+++ b/pkg/sentry/kernel/task_run.go
@@ -126,13 +126,39 @@ func (t *Task) doStop() {
 	}
 }
 
+func (*runApp) handleCPUIDInstruction(t *Task) error {
+	if len(arch.CPUIDInstruction) == 0 {
+		// CPUID emulation isn't supported, but this code can be
+		// executed, because the ptrace platform returns
+		// ErrContextSignalCPUID on page faults too. Look at
+		// pkg/sentry/platform/ptrace/ptrace.go:context.Switch for more
+		// details.
+		return platform.ErrContextSignal
+	}
+	// Is this a CPUID instruction?
+	region := trace.StartRegion(t.traceContext, cpuidRegion)
+	expected := arch.CPUIDInstruction[:]
+	found := make([]byte, len(expected))
+	_, err := t.CopyIn(usermem.Addr(t.Arch().IP()), &found)
+	if err == nil && bytes.Equal(expected, found) {
+		// Skip the cpuid instruction.
+		t.Arch().CPUIDEmulate(t)
+		t.Arch().SetIP(t.Arch().IP() + uintptr(len(expected)))
+		region.End()
+
+		return nil
+	}
+	region.End() // Not an actual CPUID, but required copy-in.
+	return platform.ErrContextSignal
+}
+
 // The runApp state checks for interrupts before executing untrusted
 // application code.
 //
 // +stateify savable
 type runApp struct{}
 
-func (*runApp) execute(t *Task) taskRunState {
+func (app *runApp) execute(t *Task) taskRunState {
 	if t.interrupted() {
 		// Checkpointing instructs tasks to stop by sending an interrupt, so we
 		// must check for stops before entering runInterrupt (instead of
@@ -237,21 +263,10 @@ func (*runApp) execute(t *Task) taskRunState {
 		return (*runApp)(nil)
 
 	case platform.ErrContextSignalCPUID:
-		// Is this a CPUID instruction?
-		region := trace.StartRegion(t.traceContext, cpuidRegion)
-		expected := arch.CPUIDInstruction[:]
-		found := make([]byte, len(expected))
-		_, err := t.CopyIn(usermem.Addr(t.Arch().IP()), &found)
-		if err == nil && bytes.Equal(expected, found) {
-			// Skip the cpuid instruction.
-			t.Arch().CPUIDEmulate(t)
-			t.Arch().SetIP(t.Arch().IP() + uintptr(len(expected)))
-			region.End()
-
+		if err := app.handleCPUIDInstruction(t); err == nil {
 			// Resume execution.
 			return (*runApp)(nil)
 		}
-		region.End() // Not an actual CPUID, but required copy-in.
 
 		// The instruction at the given RIP was not a CPUID, and we
 		// fallthrough to the default signal deliver behavior below.
diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 48c268bfa..1eeb37446 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -2663,7 +2663,9 @@ func (s *SocketOperations) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO,
 		}
 
 		// Add bytes removed from the endpoint but not yet sent to the caller.
+		s.readMu.Lock()
 		v += len(s.readView)
+		s.readMu.Unlock()
 
 		if v > math.MaxInt32 {
 			v = math.MaxInt32
diff --git a/pkg/sentry/watchdog/watchdog.go b/pkg/sentry/watchdog/watchdog.go
index bfb2fac26..f7d6009a0 100644
--- a/pkg/sentry/watchdog/watchdog.go
+++ b/pkg/sentry/watchdog/watchdog.go
@@ -221,7 +221,7 @@ func (w *Watchdog) waitForStart() {
 		return
 	}
 	var buf bytes.Buffer
-	buf.WriteString("Watchdog.Start() not called within %s:\n")
+	buf.WriteString(fmt.Sprintf("Watchdog.Start() not called within %s", w.StartupTimeout))
 	w.doAction(w.StartupTimeoutAction, false, &buf)
 }
 
@@ -325,7 +325,7 @@ func (w *Watchdog) report(offenders map[*kernel.Task]*offender, newTaskFound boo
 
 func (w *Watchdog) reportStuckWatchdog() {
 	var buf bytes.Buffer
-	buf.WriteString("Watchdog goroutine is stuck:\n")
+	buf.WriteString("Watchdog goroutine is stuck:")
 	w.doAction(w.TaskTimeoutAction, false, &buf)
 }
 
@@ -359,7 +359,7 @@ func (w *Watchdog) doAction(action Action, skipStack bool, msg *bytes.Buffer) {
 		case <-metricsEmitted:
 		case <-time.After(1 * time.Second):
 		}
-		panic(fmt.Sprintf("Stack for running G's are skipped while panicking.\n%s", msg.String()))
+		panic(fmt.Sprintf("%s\nStack for running G's are skipped while panicking.", msg.String()))
 	default:
 		panic(fmt.Sprintf("Unknown watchdog action %v", action))