Specify a memory file in platform.New().

PiperOrigin-RevId: 307941984

6 files changed, 44 insertions, 1 deletions

diff --git a/pkg/sentry/kernel/task_run.go b/pkg/sentry/kernel/task_run.go
index 2ba8d7e63..d654dd997 100644
--- a/pkg/sentry/kernel/task_run.go
+++ b/pkg/sentry/kernel/task_run.go
@@ -96,6 +96,7 @@ func (t *Task) run(threadID uintptr) {
 			t.tg.liveGoroutines.Done()
 			t.tg.pidns.owner.liveGoroutines.Done()
 			t.tg.pidns.owner.runningGoroutines.Done()
+			t.p.Release()
 
 			// Keep argument alive because stack trace for dead variables may not be correct.
 			runtime.KeepAlive(threadID)
diff --git a/pkg/sentry/platform/kvm/context.go b/pkg/sentry/platform/kvm/context.go
index c769ac7b4..6507121ea 100644
--- a/pkg/sentry/platform/kvm/context.go
+++ b/pkg/sentry/platform/kvm/context.go
@@ -85,3 +85,6 @@ func (c *context) Switch(as platform.AddressSpace, ac arch.Context, _ int32) (*a
 func (c *context) Interrupt() {
 	c.interrupt.NotifyInterrupt()
 }
+
+// Release implements platform.Context.Release().
+func (c *context) Release() {}
diff --git a/pkg/sentry/platform/kvm/kvm.go b/pkg/sentry/platform/kvm/kvm.go
index a9b4af43e..ae813e24e 100644
--- a/pkg/sentry/platform/kvm/kvm.go
+++ b/pkg/sentry/platform/kvm/kvm.go
@@ -191,6 +191,11 @@ func (*constructor) OpenDevice() (*os.File, error) {
 	return OpenDevice()
 }
 
+// Flags implements platform.Constructor.Flags().
+func (*constructor) Requirements() platform.Requirements {
+	return platform.Requirements{}
+}
+
 func init() {
 	platform.Register("kvm", &constructor{})
 }
diff --git a/pkg/sentry/platform/platform.go b/pkg/sentry/platform/platform.go
index 2ca696382..171513f3f 100644
--- a/pkg/sentry/platform/platform.go
+++ b/pkg/sentry/platform/platform.go
@@ -148,6 +148,9 @@ type Context interface {
 	// Interrupt interrupts a concurrent call to Switch(), causing it to return
 	// ErrContextInterrupt.
 	Interrupt()
+
+	// Release() releases any resources associated with this context.
+	Release()
 }
 
 var (
@@ -353,10 +356,28 @@ func (fr FileRange) String() string {
 	return fmt.Sprintf("[%#x, %#x)", fr.Start, fr.End)
 }
 
+// Requirements is used to specify platform specific requirements.
+type Requirements struct {
+	// RequiresCurrentPIDNS indicates that the sandbox has to be started in the
+	// current pid namespace.
+	RequiresCurrentPIDNS bool
+	// RequiresCapSysPtrace indicates that the sandbox has to be started with
+	// the CAP_SYS_PTRACE capability.
+	RequiresCapSysPtrace bool
+}
+
 // Constructor represents a platform type.
 type Constructor interface {
+	// New returns a new platform instance.
+	//
+	// Arguments:
+	//
+	// * deviceFile - the device file (e.g. /dev/kvm for the KVM platform).
 	New(deviceFile *os.File) (Platform, error)
 	OpenDevice() (*os.File, error)
+
+	// Requirements returns platform specific requirements.
+	Requirements() Requirements
 }
 
 // platforms contains all available platform types.
diff --git a/pkg/sentry/platform/ptrace/ptrace.go b/pkg/sentry/platform/ptrace/ptrace.go
index 03adb624b..08d055e05 100644
--- a/pkg/sentry/platform/ptrace/ptrace.go
+++ b/pkg/sentry/platform/ptrace/ptrace.go
@@ -177,6 +177,9 @@ func (c *context) Interrupt() {
 	c.interrupt.NotifyInterrupt()
 }
 
+// Release implements platform.Context.Release().
+func (c *context) Release() {}
+
 // PTrace represents a collection of ptrace subprocesses.
 type PTrace struct {
 	platform.MMapMinAddr
@@ -248,6 +251,16 @@ func (*constructor) OpenDevice() (*os.File, error) {
 	return nil, nil
 }
 
+// Flags implements platform.Constructor.Flags().
+func (*constructor) Requirements() platform.Requirements {
+	// TODO(b/75837838): Also set a new PID namespace so that we limit
+	// access to other host processes.
+	return platform.Requirements{
+		RequiresCapSysPtrace: true,
+		RequiresCurrentPIDNS: true,
+	}
+}
+
 func init() {
 	platform.Register("ptrace", &constructor{})
 }
diff --git a/pkg/sentry/platform/ptrace/subprocess.go b/pkg/sentry/platform/ptrace/subprocess.go
index a644609ef..773ddb1ed 100644
--- a/pkg/sentry/platform/ptrace/subprocess.go
+++ b/pkg/sentry/platform/ptrace/subprocess.go
@@ -332,7 +332,7 @@ func (t *thread) unexpectedStubExit() {
 	msg, err := t.getEventMessage()
 	status := syscall.WaitStatus(msg)
 	if status.Signaled() && status.Signal() == syscall.SIGKILL {
-		// SIGKILL can be only sent by an user or OOM-killer. In both
+		// SIGKILL can be only sent by a user or OOM-killer. In both
 		// these cases, we don't need to panic. There is no reasons to
 		// think that something wrong in gVisor.
 		log.Warningf("The ptrace stub process %v has been killed by SIGKILL.", t.tgid)