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Bug 1218879 - (CVE-2015-4170) CVE-2015-4170 kernel: pty layer race condition on tty ldisc shutdown.
CVE-2015-4170 kernel: pty layer race condition on tty ldisc shutdown.
Status: CLOSED ERRATA
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=20150119,repor...
: Security
Depends On: 1248302 1183479 1248300 1248301 1278751 1332164 1343555
Blocks: 1188620
  Show dependency tree / graph
 
Reported: 2015-05-06 02:29 EDT by Wade Mealing
Modified: 2016-07-12 11:14 EDT (History)
40 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
A flaw was discovered in the way the Linux kernel's TTY subsystem handled the tty shutdown phase. A local, unprivileged user could use this flaw to cause denial of service on the system by holding a reference to the ldisc lock during tty shutdown, causing a deadlock.
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Clone Of:
Environment:
Last Closed: 2016-07-12 11:14:10 EDT
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Regression: ---
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CRM:
Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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External Trackers
Tracker ID Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2015:2152 normal SHIPPED_LIVE Important: kernel security, bug fix, and enhancement update 2015-11-19 19:56:02 EST
Red Hat Product Errata RHSA-2015:2411 normal SHIPPED_LIVE Important: kernel-rt security, bug fix, and enhancement update 2015-11-19 06:24:06 EST
Red Hat Product Errata RHSA-2016:1395 normal SHIPPED_LIVE Moderate: kernel security and bug fix update 2016-07-12 09:24:59 EDT

  None (edit)
Description Wade Mealing 2015-05-06 02:29:14 EDT 
An issue was discovered in the linux kernel's tty subsystem handling during shutdown. The flaw was possible to take a reference to the ldisc during shutdown phase.

This race occurs on hangup of tty.  It races and hangs on ldsem_down_write on a semaphore that is being aquired by a new reader(CPU 1).  The new reader/writer is sleeping in ldsem_down_read() and the hangup is sleeping in ldsem_down_write().

Resources:

Fix: http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=cf872776fc84128bb779ce2b83a37c884c3203ae
CVE request: http://seclists.org/oss-sec/2015/q2/545
Comment 1 Wade Mealing 2015-05-28 00:04:48 EDT 
Statement:

This issue does not affect the Linux kernels as shipped with Red Hat Enterprise Linux 5, 6.

This issue affects the Linux kernel packages kernel as shipped with Red Hat Enterprise Linux 7 and Red Hat Enterprise MRG 2.
Comment 7 errata-xmlrpc 2015-11-19 08:19:22 EST 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2411 https://rhn.redhat.com/errata/RHSA-2015-2411.html
Comment 8 errata-xmlrpc 2015-11-19 17:15:15 EST 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2152 https://rhn.redhat.com/errata/RHSA-2015-2152.html
Comment 11 errata-xmlrpc 2016-07-12 05:25:14 EDT 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.1 Extended Update Support

Via RHSA-2016:1395 https://access.redhat.com/errata/RHSA-2016:1395
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