1 files changed, 17 insertions, 11 deletions
diff --git a/pkg/sentry/kernel/sessions.go b/pkg/sentry/kernel/sessions.go
index ca9076406..f9f872522 100644
--- a/pkg/sentry/kernel/sessions.go
+++ b/pkg/sentry/kernel/sessions.go
@@ -16,7 +16,7 @@ package kernel
 
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 )
 
 // SessionID is the public identifier.
@@ -120,8 +120,9 @@ func (pg *ProcessGroup) Originator() *ThreadGroup {
 
 // IsOrphan returns true if this process group is an orphan.
 func (pg *ProcessGroup) IsOrphan() bool {
-	pg.originator.TaskSet().mu.RLock()
-	defer pg.originator.TaskSet().mu.RUnlock()
+	ts := pg.originator.TaskSet()
+	ts.mu.RLock()
+	defer ts.mu.RUnlock()
 	return pg.ancestors == 0
 }
 
@@ -277,14 +278,14 @@ func (tg *ThreadGroup) createSession() error {
 			continue
 		}
 		if s.leader == tg {
-			return syserror.EPERM
+			return linuxerr.EPERM
 		}
 		if s.id == SessionID(id) {
-			return syserror.EPERM
+			return linuxerr.EPERM
 		}
 		for pg := s.processGroups.Front(); pg != nil; pg = pg.Next() {
 			if pg.id == ProcessGroupID(id) {
-				return syserror.EPERM
+				return linuxerr.EPERM
 			}
 		}
 	}
@@ -369,17 +370,22 @@ func (tg *ThreadGroup) CreateProcessGroup() error {
 	// Get the ID for this thread in the current namespace.
 	id := tg.pidns.tgids[tg]
 
+	// Check whether a process still exists or not.
+	if id == 0 {
+		return linuxerr.ESRCH
+	}
+
 	// Per above, check for a Session leader or existing group.
 	for s := tg.pidns.owner.sessions.Front(); s != nil; s = s.Next() {
 		if s.leader.pidns != tg.pidns {
 			continue
 		}
 		if s.leader == tg {
-			return syserror.EPERM
+			return linuxerr.EPERM
 		}
 		for pg := s.processGroups.Front(); pg != nil; pg = pg.Next() {
 			if pg.id == ProcessGroupID(id) {
-				return syserror.EPERM
+				return linuxerr.EPERM
 			}
 		}
 	}
@@ -437,17 +443,17 @@ func (tg *ThreadGroup) JoinProcessGroup(pidns *PIDNamespace, pgid ProcessGroupID
 	// Lookup the ProcessGroup.
 	pg := pidns.processGroups[pgid]
 	if pg == nil {
-		return syserror.EPERM
+		return linuxerr.EPERM
 	}
 
 	// Disallow the join if an execve has performed, per POSIX.
 	if checkExec && tg.execed {
-		return syserror.EACCES
+		return linuxerr.EACCES
 	}
 
 	// See if it's in the same session as ours.
 	if pg.session != tg.processGroup.session {
-		return syserror.EPERM
+		return linuxerr.EPERM
 	}
 
 	// Join the group; adjust children.