Bug 844714 - (CVE-2012-3412) CVE-2012-3412 kernel: sfc: potential remote denial of service through TCP MSS option
CVE-2012-3412 kernel: sfc: potential remote denial of service through TCP MSS...
Status: CLOSED ERRATA
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
high Severity high
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Assigned To: Red Hat Product Security
impact=important,public=20120730,repo...
: Security
Depends On: 845554 845555 845556 845557 845558 852354 852355 852356
Blocks: 844716
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Reported: 2012-07-31 09:27 EDT by Petr Matousek
Modified: 2015-07-31 06:06 EDT (History)
23 users (show)

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Doc Type: Bug Fix
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Last Closed: 2013-08-24 08:25:23 EDT
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RHEL 7.3 requirements from Atomic Host:
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Description Petr Matousek 2012-07-31 09:27:49 EDT
A peer (or local user) may cause TCP to use a nominal MSS of as little
as 88 (actual MSS of 76 with timestamps).  Given that we have a
sufficiently prodigious local sender and the peer ACKs quickly enough,
it is nevertheless possible to grow the window for such a connection
to the point that we will try to send just under 64K at once.  This
results in a single skb that expands to 861 segments.

In some drivers with TSO support, such an skb will require hundreds of
DMA descriptors; a substantial fraction of a TX ring or even more than
a full ring.  The TX queue selected for the skb may stall and trigger
the TX watchdog repeatedly (since the problem skb will be retried
after the TX reset).

Upstream patch:
http://www.spinics.net/lists/netdev/msg206332.html

References:
http://seclists.org/oss-sec/2012/q3/171

Acknowledgements:

Red Hat would like to thank Ben Hutchings of Solarflare (tm) for reporting this issue.
Comment 3 Petr Matousek 2012-08-03 08:35:31 EDT
Created kernel tracking bugs for this issue

Affects: fedora-all [bug 845558]
Comment 6 Petr Matousek 2012-08-03 12:46:54 EDT
Mitigation as recommended by Ben Hutchings
------------------------------------------

If all processes that may send on the sfc interface use Onload, or do
not use TCP, the vulnerability does not exist.

The vulnerability can otherwise be avoided by making a temporary
configuration change.  For an sfc interface named eth0, either:

a. Increase the TX queue size:
       ethtool -G eth0 tx 4096
   This can increase TX latency and memory usage.

or:

b. Disable TSO:
       ethtool -K eth0 tso off
   This can reduce TX throughput and/or increase CPU usage.
Comment 9 errata-xmlrpc 2012-10-02 13:11:36 EDT
This issue has been addressed in following products:

  RHEV-H, V2V and Agents for RHEL-5

Via RHSA-2012:1324 https://rhn.redhat.com/errata/RHSA-2012-1324.html
Comment 10 errata-xmlrpc 2012-10-02 13:45:30 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2012:1323 https://rhn.redhat.com/errata/RHSA-2012-1323.html
Comment 11 errata-xmlrpc 2012-10-09 06:28:53 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5.6 EUS - Server Only

Via RHSA-2012:1347 https://rhn.redhat.com/errata/RHSA-2012-1347.html
Comment 12 errata-xmlrpc 2012-10-16 10:46:08 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2012:1366 https://rhn.redhat.com/errata/RHSA-2012-1366.html
Comment 13 errata-xmlrpc 2012-10-18 12:46:58 EDT
This issue has been addressed in following products:

  RHEV-H and Agents for RHEL-6

Via RHSA-2012:1375 https://rhn.redhat.com/errata/RHSA-2012-1375.html
Comment 14 errata-xmlrpc 2012-10-23 14:11:32 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6.2 EUS - Server Only

Via RHSA-2012:1401 https://rhn.redhat.com/errata/RHSA-2012-1401.html
Comment 15 errata-xmlrpc 2012-11-06 13:06:34 EST
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6.1 EUS - Server Only

Via RHSA-2012:1430 https://rhn.redhat.com/errata/RHSA-2012-1430.html

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