kernel-packages team mailing list archive

[Seth Forshee <seth.forshee+lp@xxxxxxxxxxxxx>]

On Tue, Jan 12, 2016 at 05:16:28PM -0000, Serge Hallyn wrote:
> in ovl_clear_empty(), the opaque bit is set on the dir in workingdir
> 
> in ovl_create_over_whiteout() (the case we're currently looking at) it is
> also being set in the working dir.
> 
> in ovl_rename2(), it is set in two places, on the upper dentries for
> both the old and new.
> 
> So it is never set on the lowerdir, at least.

Ah. So if it's never set on the lowerdir that does remove much of the
concern.

> I'm still looking, but it may be safe to say that all needed inode
> checks are already done before we call ovl_set_opaque() so that we
> can indeed just use prepare_kernel_cred(NULL) instead of prepare_cred().

Cool.

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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1531747

Title:
  overlay: mkdir fails if directory exists in lowerdir in a user
  namespace

Status in linux package in Ubuntu:
  Triaged
Status in linux source package in Wily:
  Triaged
Status in linux source package in Xenial:
  Triaged

Bug description:
  If a directory exists in the lowerdir but not in the mounted
  overlay, then mkdir of the directory in the target dir results
  in a mysterious -EPERM.  I've seen this both in wily kernel
  (4.2.0-22-generic #27-Ubuntu) and in a hand-built xenial
  master-next (with unrelated patches added).

  =====================================================
  #!/bin/sh -ex
  dir=`mktemp -d`
  cleanup() {
   umount -l $dir/t
   rm -rf $dir
  }

  trap cleanup EXIT

  echo "dir is $dir"
  mkdir -p $dir/l $dir/u $dir/w $dir/t
  mkdir $dir/l/dev
  mount -t overlay -o lowerdir=$dir/l,upperdir=$dir/u,workdir=$dir/w o $dir/t
  stat $dir/t/dev
  rmdir $dir/t/dev
  mkdir $dir/t/dev
  echo $?
  echo "mkdir should have succeeded"
  =====================================================

  The above will work on the host, but fail in a user namespace, i.e
  in a regular lxd container.

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