Iirc, as of 4.8 what you're seeing is upstream behavior, and yes it did get backported to xenial in the series you referenced.
Even if the inode is created with INVALID_UID/INVALID_GID you aren't going to be able to do anything with it. So I guess the question is why you need to be able to do that and whether or not you can accomplish that some other way. If not then the behavior would need to change upstream - even if we fix it in xenial 4.4 kernels you'll probably just hit it again later. Note that you don't actually need to enter the user namespace to create the file, you just need fsuid/fsgid to be ids which have a mapping in the user ns. -- 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/1659087 Title: open(2) returns EOVERFLOW within tmpfs+userns Status in linux package in Ubuntu: Confirmed Bug description: On Ubuntu 4.4.0-59.80-generic 4.4.35, open(2) returns EOVERFLOW when creating a file in tmpfs with user namespace enabled. This issue wasn't present in 4.4.0-47 and has probably been introduced by https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1634964 Step to reproduce: $ unshare -r -U -m /bin/bash # mount -t tmpfs tmpfs /mnt # echo $$ 2354 In another terminal: $ sudo nsenter -t 2354 -m # touch /mnt/foo touch: cannot touch '/mnt/foo': Value too large for defined data type Note that we are not joining the user namespace when creating the file but we would expect `touch' to succeed and create the file with an inode set to INVALID_UID/GID (i.e. nobody:nogroup) within the mount namespace. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1659087/+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
