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, 6 insertions, 2 deletions

diff --git a/pkg/sentry/fsimpl/proc/task.go b/pkg/sentry/fsimpl/proc/task.go
index a5c7aa470..109b31b4c 100644
--- a/pkg/sentry/fsimpl/proc/task.go
+++ b/pkg/sentry/fsimpl/proc/task.go
@@ -105,7 +105,9 @@ func (i *taskInode) Valid(ctx context.Context) bool {
 
 // Open implements kernfs.Inode.
 func (i *taskInode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts, kernfs.GenericDirectoryFDOptions{
+		SeekEnd: kernfs.SeekEndZero,
+	})
 	if err != nil {
 		return nil, err
 	}
@@ -142,7 +144,9 @@ func (fs *filesystem) newTaskOwnedDir(task *kernel.Task, ino uint64, perm linux.
 	dir := &kernfs.StaticDirectory{}
 
 	// Note: credentials are overridden by taskOwnedInode.
-	dir.Init(task.Credentials(), linux.UNNAMED_MAJOR, fs.devMinor, ino, perm)
+	dir.Init(task.Credentials(), linux.UNNAMED_MAJOR, fs.devMinor, ino, perm, kernfs.GenericDirectoryFDOptions{
+		SeekEnd: kernfs.SeekEndZero,
+	})
 
 	inode := &taskOwnedInode{Inode: dir, owner: task}
 	d := &kernfs.Dentry{}