Fix seek on /proc/pid/cmdline when task is zombie.

PiperOrigin-RevId: 348056159

1 files changed, 11 insertions, 6 deletions

diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index a3780b222..75be6129f 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -57,9 +57,6 @@ func getMM(task *kernel.Task) *mm.MemoryManager {
 // MemoryManager's users count is incremented, and must be decremented by the
 // caller when it is no longer in use.
 func getMMIncRef(task *kernel.Task) (*mm.MemoryManager, error) {
-	if task.ExitState() == kernel.TaskExitDead {
-		return nil, syserror.ESRCH
-	}
 	var m *mm.MemoryManager
 	task.WithMuLocked(func(t *kernel.Task) {
 		m = t.MemoryManager()
@@ -111,9 +108,13 @@ var _ dynamicInode = (*auxvData)(nil)
 
 // Generate implements vfs.DynamicBytesSource.Generate.
 func (d *auxvData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	if d.task.ExitState() == kernel.TaskExitDead {
+		return syserror.ESRCH
+	}
 	m, err := getMMIncRef(d.task)
 	if err != nil {
-		return err
+		// Return empty file.
+		return nil
 	}
 	defer m.DecUsers(ctx)
 
@@ -157,9 +158,13 @@ var _ dynamicInode = (*cmdlineData)(nil)
 
 // Generate implements vfs.DynamicBytesSource.Generate.
 func (d *cmdlineData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	if d.task.ExitState() == kernel.TaskExitDead {
+		return syserror.ESRCH
+	}
 	m, err := getMMIncRef(d.task)
 	if err != nil {
-		return err
+		// Return empty file.
+		return nil
 	}
 	defer m.DecUsers(ctx)
 
@@ -472,7 +477,7 @@ func (fd *memFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64
 	}
 	m, err := getMMIncRef(fd.inode.task)
 	if err != nil {
-		return 0, nil
+		return 0, err
 	}
 	defer m.DecUsers(ctx)
 	// Buffer the read data because of MM locks