FreeBSD : FreeBSD -- Cross-mount links between nullfs(5) mounts (b72bad1c-20ed-11e3-be06-000c29ee3065)
Low Nessus Plugin ID 70263
SynopsisThe remote FreeBSD host is missing one or more security-related updates.
DescriptionProblem Description :
The nullfs(5) implementation of the VOP_LINK(9) VFS operation does not check whether the source and target of the link are both in the same nullfs instance. It is therefore possible to create a hardlink from a location in one nullfs instance to a file in another, as long as the underlying (source) filesystem is the same.
If multiple nullfs views into the same filesystem are mounted in different locations, a user with read access to one of these views and write access to another will be able to create a hard link from the latter to a file in the former, even though they are, from the user's perspective, different filesystems. The user may thereby gain write access to files which are nominally on a read-only filesystem.
SolutionUpdate the affected packages.