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, 6 insertions, 63 deletions

diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index e830cf948..c0ab53c94 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -21,7 +21,6 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/bpf"
-	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
@@ -29,11 +28,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/sched"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
-	"gvisor.dev/gvisor/pkg/sentry/limits"
-	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
-	"gvisor.dev/gvisor/pkg/sentry/unimpl"
-	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
@@ -63,6 +58,12 @@ import (
 type Task struct {
 	taskNode
 
+	// goid is the task goroutine's ID. goid is owned by the task goroutine,
+	// but since it's used to detect cases where non-task goroutines
+	// incorrectly access state owned by, or exclusive to, the task goroutine,
+	// goid is always accessed using atomic memory operations.
+	goid int64 `state:"nosave"`
+
 	// runState is what the task goroutine is executing if it is not stopped.
 	// If runState is nil, the task goroutine should exit or has exited.
 	// runState is exclusive to the task goroutine.
@@ -641,64 +642,6 @@ func (t *Task) Kernel() *Kernel {
 	return t.k
 }
 
-// Value implements context.Context.Value.
-//
-// Preconditions: The caller must be running on the task goroutine (as implied
-// by the requirements of context.Context).
-func (t *Task) Value(key interface{}) interface{} {
-	switch key {
-	case CtxCanTrace:
-		return t.CanTrace
-	case CtxKernel:
-		return t.k
-	case CtxPIDNamespace:
-		return t.tg.pidns
-	case CtxUTSNamespace:
-		return t.utsns
-	case CtxIPCNamespace:
-		ipcns := t.IPCNamespace()
-		ipcns.IncRef()
-		return ipcns
-	case CtxTask:
-		return t
-	case auth.CtxCredentials:
-		return t.Credentials()
-	case context.CtxThreadGroupID:
-		return int32(t.ThreadGroup().ID())
-	case fs.CtxRoot:
-		return t.fsContext.RootDirectory()
-	case vfs.CtxRoot:
-		return t.fsContext.RootDirectoryVFS2()
-	case vfs.CtxMountNamespace:
-		t.mountNamespaceVFS2.IncRef()
-		return t.mountNamespaceVFS2
-	case fs.CtxDirentCacheLimiter:
-		return t.k.DirentCacheLimiter
-	case inet.CtxStack:
-		return t.NetworkContext()
-	case ktime.CtxRealtimeClock:
-		return t.k.RealtimeClock()
-	case limits.CtxLimits:
-		return t.tg.limits
-	case pgalloc.CtxMemoryFile:
-		return t.k.mf
-	case pgalloc.CtxMemoryFileProvider:
-		return t.k
-	case platform.CtxPlatform:
-		return t.k
-	case uniqueid.CtxGlobalUniqueID:
-		return t.k.UniqueID()
-	case uniqueid.CtxGlobalUniqueIDProvider:
-		return t.k
-	case uniqueid.CtxInotifyCookie:
-		return t.k.GenerateInotifyCookie()
-	case unimpl.CtxEvents:
-		return t.k
-	default:
-		return nil
-	}
-}
-
 // SetClearTID sets t's cleartid.
 //
 // Preconditions: The caller must be running on the task goroutine.