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Message #155491
[Bug 1531747] Re: overlay: mkdir fails if directory exists in lowerdir in a user namespace
hat may not be ok for the ovl_rename2 case.
What we want is for inode permissions to be checked, but only the
bit in xattr_permission() checking for trusted.* to accept ns_capable.
We could special-case that in xattr_permission(), but that's not
particularly nice.
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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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References