fs/namespace.c in the Linux kernel before 4.0.2 processes MNT_DETACH umount2...

Vulnerability Description

fs/namespace.c in the Linux kernel before 4.0.2 processes MNT_DETACH umount2 system calls without verifying that the MNT_LOCKED flag is unset, which allows local users to bypass intended access restrictions and navigate to filesystem locations beneath a mount by calling umount2 within a user namespace.

References

• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00054.html
• http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00056.html
• https://github.com/torvalds/linux/commit/ce07d891a0891d3c0d0c2d73d577490486b809e1
• http://www.openwall.com/lists/oss-security/2015/04/17/4
• http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=ce07d891a0891d3c0d0c2d73d577490486b809e1
• https://bugzilla.redhat.com/show_bug.cgi?id=1226751
• https://groups.google.com/forum/message/raw?msg=linux.kernel/HnegnbXk0Vs/RClojwJzAFEJ
• http://www.spinics.net/lists/linux-containers/msg30786.html
• http://www.securityfocus.com/bid/74226
• http://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.0.2
• http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00000.html