It was found that in Linux kernel the mount table expands by a power-of-two with each bind mount command. If a system is configured to allow non-privileged user to do bind mounts, or allows to do so in a container or unprivileged mount namespace, then non-privileged user is able to cause a local DoS by overflowing the mount table, which causes a deadlock for the whole system. CVE request: http://seclists.org/oss-sec/2016/q3/56 Proofs: http://seclists.org/oss-sec/2016/q3/65 http://seclists.org/oss-sec/2016/q3/75 Discussions: https://lkml.org/lkml/2013/6/17/143
Acknowledgments: Name: Qian Cai (Red Hat)
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1356472]
It seems there is some debate on whether the CVE is actually something the kernel needs to fix. I'll hold off a bit on this one.
Another reproducer using Docker: http://seclists.org/oss-sec/2016/q3/65
Another reproducer which doesn't use Docker, but it needs user namespaces to be enabled: http://seclists.org/oss-sec/2016/q3/75
I've reported this problem two years ago https://lkml.org/lkml/2013/6/20/709
(In reply to Andrew Vagin from comment #6) > I've reported this problem two years ago > https://lkml.org/lkml/2013/6/20/709 It's actually three years ago.
Statement: This issue does not affect the Linux kernel packages as shipped with Red Hat Enterprise Linux 5, 6, 7 and MRG-2 as of now due to the absence of unprivileged mount name spaces support. Nevertheless, the unprivileged mount name spaces might be added to a future RHEL-7 version as a supported feature, so future Linux kernel updates for the respective releases might address this issue.
https://lkml.org/lkml/2016/8/28/269
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2017:2077 https://access.redhat.com/errata/RHSA-2017:2077
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2017:1842 https://access.redhat.com/errata/RHSA-2017:1842