Clarify seek behaviour for kernfs.GenericDirectoryFD.

- Remove comment about GenericDirectoryFD not being compatible with
  dynamic directories. It is currently being used to implement dynamic
  directories.

- Try to handle SEEK_END better than setting the offset to
  infinity. SEEK_END is poorly defined for dynamic directories
  anyways, so at least try make it work correctly for the static
  entries.

Updates #1193.

PiperOrigin-RevId: 327890128

1 files changed, 3 insertions, 1 deletions

diff --git a/pkg/sentry/fsimpl/proc/subtasks.go b/pkg/sentry/fsimpl/proc/subtasks.go
index 79c2725f3..f25747da3 100644
--- a/pkg/sentry/fsimpl/proc/subtasks.go
+++ b/pkg/sentry/fsimpl/proc/subtasks.go
@@ -155,7 +155,9 @@ func (fd *subtasksFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) erro
 // Open implements kernfs.Inode.
 func (i *subtasksInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
 	fd := &subtasksFD{task: i.task}
-	if err := fd.Init(&i.OrderedChildren, &i.locks, &opts); err != nil {
+	if err := fd.Init(&i.OrderedChildren, &i.locks, &opts, kernfs.GenericDirectoryFDOptions{
+		SeekEnd: kernfs.SeekEndZero,
+	}); err != nil {
 		return nil, err
 	}
 	if err := fd.VFSFileDescription().Init(fd, opts.Flags, rp.Mount(), vfsd, &vfs.FileDescriptionOptions{}); err != nil {