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Bug 1568744 - (CVE-2018-1000200) CVE-2018-1000200 kernel: NULL pointer dereference on OOM kill of large mlocked process
CVE-2018-1000200 kernel: NULL pointer dereference on OOM kill of large mlocke...
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20180424,repor...
: Security
Depends On: 1570542 1571595 1571596
Blocks: 1568749
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Reported: 2018-04-18 04:29 EDT by Adam Mariš
Modified: 2018-10-30 05:00 EDT (History)
44 users (show)

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A flaw was found in the Linux kernel where an out of memory (oom) killing of a process that has large spans of mlocked memory can result in deferencing a NULL pointer, leading to denial of service.
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External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2018:2948 None None None 2018-10-30 05:00 EDT

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Description Adam Mariš 2018-04-18 04:29:27 EDT 
It was found that out of memory (oom) killing a process that has large spans of mlocked memory can result in deferencing a NULL pointer, leading to denial of service.

The issue arises from an oom killed process's final thread calling exit_mmap(), which calls munlock_vma_pages_all() for mlocked vmas.  This can happen synchronously with the oom reaper's unmap_page_range() since the vma's VM_LOCKED bit is cleared before munlocking (to determine if any other vmas share the memory and are mlocked).

References: 

https://marc.info/?l=linux-kernel&m=152400522806945

https://marc.info/?l=linux-kernel&m=152460926619256

http://seclists.org/oss-sec/2018/q2/67

Introduced by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=212925802454672e6cd2949a727f5e2c1377bf06

An upstream patch:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=27ae357fa82be5ab73b2ef8d39dcb8ca2563483a
Comment 1 Adam Mariš 2018-04-18 04:29:30 EDT 
Acknowledgments:

Name: David Rientjes (Google)
Comment 6 Adam Mariš 2018-04-25 03:58:22 EDT 
Public via:

http://seclists.org/oss-sec/2018/q2/67
Comment 7 Adam Mariš 2018-04-25 03:59:21 EDT 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1571596]
Comment 9 Justin M. Forbes 2018-04-25 08:17:05 EDT 
This was fixed for Fedora with the 4.15 rebases
Comment 12 errata-xmlrpc 2018-10-30 05:00:04 EDT 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2018:2948 https://access.redhat.com/errata/RHSA-2018:2948
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