Thank you for the detailed explanation. Since the underlying problem is that overlayfs is not (yet very) namespace aware, this issue may be intractable.
Naive question regarding copy-up: Do the files in the upperdir and lowerdir need to have the same owner? If not, could copy-up be amended so that it behaves similarly to the copying of a root-owned file by a non-root user? Ie the ownership of the file in the upperdir could change to that of the user doing the copying/deleting. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1617388 Title: When using overlayfs with kernel 4.4, some files cannot be deleted. Status in linux package in Ubuntu: Triaged Bug description: #!/bin/bash # --------------------------------------------------------------------- # This script exhibits a bug in overlayfs in kernel 4.4. # The bug is not present in kernel 4.2. # The bug can be reproduced in an x86_64 virtual-machine; # 32-bit has not been tested. # # With kernel 4.2, the script output ends with: # "script completed without encountering a kernel bug" # # With kernel 4.4, the script output ends with: # "rm: cannot remove ‘mnt_ovl/sub/sub.txt’: # Value too large for defined data type" # # The script depends upon lxc-usernsexec (part of the lxc1 package) to # create a user-namespace. # # The script should be run as a normal user (not root), in a directory where # the user has write-permission: # ./script # -------------------------------------------------------------------- cleanup() { [[ -d "$storedir" ]] || exit 1 cd "$storedir" || exit 1 [[ -d "$tmpdir" ]] || exit 1 lxc-usernsexec -m b:0:1000:1 -m b:100000:100000:1 -- rm -rf "$tmpdir" } trap cleanup EXIT set -e storedir="$(pwd)" # create tmpdir tmpdir="$(mktemp -d --tmpdir=.)" cd "$tmpdir" # create lowerdir for overlay mkdir -p lower/sub touch lower/lower.txt lower/sub/sub.txt cd .. chmod -R a+rwX "$tmpdir" # run a script in a user namepace lxc-usernsexec -m b:0:100000:65534 -- bash << EOF set -e cd "$tmpdir" # create tmpfs mkdir mnt_tmpfs mount -t tmpfs tmpfs mnt_tmpfs # create upperdir and workdir for overlay mkdir mnt_tmpfs/{upper,work} # mount overlay mkdir mnt_ovl mount -t overlay \ -o lowerdir=lower,upperdir=mnt_tmpfs/upper,workdir=mnt_tmpfs/work \ overlay mnt_ovl echo 'overlay directory listing' ls -RF mnt_ovl echo '' set -x rm mnt_ovl/lower.txt # always succeeds rm mnt_ovl/sub/sub.txt # fails with kernel 4.4+ set +x echo 'script completed without encountering a kernel bug' EOF To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1617388/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
