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[oleg <1531747@xxxxxxxxxxxxxxxxxx>]

FWIW, bug #1480411, "rm -r * fails to delete directories when using
overlayfs in a user-namespace", might be a duplicate of this bug.   In
both bugs the script works on the host but fails in a user-namespace
with error EPERM.  In this bug the operation which triggers the error is
'mkdir', while in bug #1480411 it is 'rmdir'.

The equivalent script for bug #1480411 is,

#================================
#!/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
touch $dir/l/dev/foo.txt
mount -t overlay -o lowerdir=$dir/l,upperdir=$dir/u,workdir=$dir/w o $dir/t
stat $dir/t/dev
rm $dir/t/dev/foo.txt
rmdir $dir/t/dev
echo $?
echo "rmdir should have succeeded"
#===================================

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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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