Check for misuse of kernel.Task as context.Context.

Checks in Task.block() and Task.Value() are conditional on race detection being
enabled, since these functions are relatively hot. Checks in Task.SleepStart()
and Task.UninterruptibleSleepStart() are enabled unconditionally, since these
functions are not thought to lie on any critical paths, and misuse of these
functions is required for b/168241471 to manifest.

PiperOrigin-RevId: 342342175

1 files changed, 15 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/task_run.go b/pkg/sentry/kernel/task_run.go
index 0f8294dcd..c5858da30 100644
--- a/pkg/sentry/kernel/task_run.go
+++ b/pkg/sentry/kernel/task_run.go
@@ -16,11 +16,13 @@ package kernel
 
 import (
 	"bytes"
+	"fmt"
 	"runtime"
 	"runtime/trace"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/goid"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/hostcpu"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
@@ -57,6 +59,8 @@ type taskRunState interface {
 // make it visible in stack dumps. A goroutine for a given task can be identified
 // searching for Task.run()'s argument value.
 func (t *Task) run(threadID uintptr) {
+	atomic.StoreInt64(&t.goid, goid.Get())
+
 	// Construct t.blockingTimer here. We do this here because we can't
 	// reconstruct t.blockingTimer during restore in Task.afterLoad(), because
 	// kernel.timekeeper.SetClocks() hasn't been called yet.
@@ -99,6 +103,9 @@ func (t *Task) run(threadID uintptr) {
 			t.tg.pidns.owner.runningGoroutines.Done()
 			t.p.Release()
 
+			// Deferring this store triggers a false positive in the race
+			// detector (https://github.com/golang/go/issues/42599).
+			atomic.StoreInt64(&t.goid, 0)
 			// Keep argument alive because stack trace for dead variables may not be correct.
 			runtime.KeepAlive(threadID)
 			return
@@ -375,6 +382,14 @@ func (app *runApp) execute(t *Task) taskRunState {
 	}
 }
 
+// assertTaskGoroutine panics if the caller is not running on t's task
+// goroutine.
+func (t *Task) assertTaskGoroutine() {
+	if got, want := goid.Get(), atomic.LoadInt64(&t.goid); got != want {
+		panic(fmt.Sprintf("running on goroutine %d (task goroutine for kernel.Task %p is %d)", got, t, want))
+	}
+}
+
 // waitGoroutineStoppedOrExited blocks until t's task goroutine stops or exits.
 func (t *Task) waitGoroutineStoppedOrExited() {
 	t.goroutineStopped.Wait()