|Summary:||CVE-2016-6213 kernel: Overflowing kernel mount table using shared bind mount|
|Product:||[Other] Security Response||Reporter:||Adam Mariš <amaris>|
|Component:||vulnerability||Assignee:||Red Hat Product Security <security-response-team>|
|Status:||CLOSED ERRATA||QA Contact:|
|Version:||unspecified||CC:||aquini, arm-mgr, avagin, bhu, caiqian, carnil, dhoward, fhrbata, gansalmon, iboverma, itamar, jforbes, jkacur, joelsmith, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, kir, kstutsma, labbott, lgoncalv, madhu.chinakonda, matt, mchehab, mcressma, nmurray, plougher, rt-maint, rvrbovsk, slawomir, vdronov, williams|
|Fixed In Version:||Doc Type:||Bug Fix|
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.
|Last Closed:||2019-06-08 02:56:15 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
|Bug Depends On:||1322495, 1356472|
|Bug Blocks:||1332565, 1356474|
Description Adam Mariš 2016-07-14 08:09:18 UTC
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
Comment 1 Adam Mariš 2016-07-14 08:09:39 UTC
Acknowledgments: Name: Qian Cai (Red Hat)
Comment 2 Adam Mariš 2016-07-14 08:10:10 UTC
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1356472]
Comment 3 Josh Boyer 2016-07-14 13:08:54 UTC
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.
Comment 4 Adam Mariš 2016-07-15 06:58:43 UTC
Another reproducer using Docker: http://seclists.org/oss-sec/2016/q3/65
Comment 5 Andrej Nemec 2016-07-18 06:55:03 UTC
Another reproducer which doesn't use Docker, but it needs user namespaces to be enabled: http://seclists.org/oss-sec/2016/q3/75
Comment 6 Andrew Vagin 2016-07-22 00:05:46 UTC
I've reported this problem two years ago https://lkml.org/lkml/2013/6/20/709
Comment 7 Kir Kolyshkin 2016-07-28 18:02:27 UTC
(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.
Comment 9 Vladis Dronov 2016-08-30 13:50:21 UTC
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.
Comment 11 errata-xmlrpc 2017-08-01 19:08:48 UTC
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