This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed- cosmic' to 'verification-done-cosmic'. If the problem still exists, change the tag 'verification-needed-cosmic' to 'verification-failed- cosmic'.
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-cosmic -- 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/1801924 Title: CVE-2018-18955: nested user namespaces with more than five extents incorrectly grant privileges over inode Status in linux package in Ubuntu: Triaged Status in linux source package in Bionic: Fix Committed Status in linux source package in Cosmic: Fix Committed Status in linux source package in Disco: Triaged Bug description: Jann Horn reported that nested user namespaces with more than five mappings allow gaining privilege over an inode. Here is my write up of how this happens: Currently, the forward map and reverse map are copied and sorted at the same time before necessary updates to the forward map have been performed. This has the consequence that the forward map receives the necessary updates while the reverse map does not leaving it with invalid data. Specifically, this means that the lower ids of the forward mapping will be correctly mapped to appropriate kernel ids, while the lower ids of the reverse mapping will not. This breaks inode_owner_or_capable() and privileged_wrt_inode_uidgid() which call helpers that need to access the reverse mapping. Thus, a process can incorrectly appear to be capable relative to an inode. Note that the sorting logic is only triggered when more than five extents are specified and when user namespaces are nested. Hence, only containers with complex mappings in nested user namespaces are affected. To fix this issue we need to ensures that the translation happens for both the forward and reverse mappings. First, the forward mappings are sorted and its lower ids translated into kernel ids. After this the forward mapping is copied and into the reverse mapping and the reverse mappings sorted. A proposed patch is appended here. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1801924/+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
