Glad you figured it out, I suspected this had something to do with the may_create/may_o_create code paths but couldn't wrap my head around it. Hopefully this will be addressed upstream in the near future.
This change in behavior is surprising though, maybe this should be documented in user_namespaces(7). -- 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 Status in linux source package in Xenial: 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
