Bug 697822 - (CVE-2011-1593) CVE-2011-1593 kernel: proc: signedness issue in next_pidmap()
CVE-2011-1593 kernel: proc: signedness issue in next_pidmap()
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
public=20110413,reported=20110413,sou...
: Security
Depends On: 697824 697825 697826 697827 697828 697838
Blocks:
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Reported: 2011-04-19 07:42 EDT by Petr Matousek
Modified: 2015-07-29 13:47 EDT (History)
14 users (show)

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Doc Type: Bug Fix
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Last Closed: 2015-07-29 08:39:47 EDT
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Description Petr Matousek 2011-04-19 07:42:20 EDT
A signedness issue has been found in next_pidmap() function when the "last"
parameter is negative as next_pidmap() just quietly accepted whatever
"last" pid that was passed in, which is not all that safe when one of the
users is /proc.

Setting f_pos to negative value when accessing /proc via readdir()/getdents()
resulted in sign extension of this value when map pointer was being
constructed.

This later lead to #GP becasue the final pointer was not cannonical (x86_64).

map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE];
 ffffffff810ac3b4:       48 63 f6                movslq %esi,%rsi      <- sign extension (f_pos+-)
 ffffffff810ac3b7:       81 e2 ff 7f 00 00       and    $0x7fff,%edx 
 ffffffff810ac3bd:       48 c1 ee 0f             shr    $0xf,%rsi
 ffffffff810ac3c1:       48 c1 e6 04             shl    $0x4,%rsi
 ffffffff810ac3c5:       48 8d 5c 37 08          lea    0x8(%rdi,%rsi,1),%rbx 
  ...
if (unlikely(!map->page)) 
 ffffffff810ac3cc:       48 8b 7b 08             mov    0x8(%rbx),%rdi <- #GP

Only x86_64 architecture seems to be vulnerable to this particular issue
(tested ppc64, s390x, ia64).

Reference:
http://groups.google.com/group/fa.linux.kernel/browse_thread/thread/93c1088451fd3522/4a28ecb7f755a88d?#4a28ecb7f755a88d

Upstream commit:
http://git.kernel.org/linus/c78193e9
http://git.kernel.org/linus/d8bdc59f

Acknowledgements:

Red Hat would like to thank Robert Swiecki for reporting this issue.
Comment 5 Petr Matousek 2011-05-02 05:58:00 EDT
Statement:

This issue affects the versions of Linux kernel as shipped with Red Hat
Enterprise Linux 4, 5, 6, and Red Hat Enterprise MRG. This has been addressed in Red Hat Enterprise Linux 5, 6 and Red Hat Enterprise MRG via https://rhn.redhat.com/errata/RHSA-2011-0927.html, https://rhn.redhat.com/errata/RHSA-2011-1189.html, and https://rhn.redhat.com/errata/RHSA-2011-1253.html. Red Hat Enterprise Linux 4 is now in Production 3 of the maintenance life-cycle, https://access.redhat.com/support/policy/updates/errata/, therefore the fix for this issue is not currently planned to be included in the future updates.
Comment 6 errata-xmlrpc 2011-07-15 02:09:03 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 5

Via RHSA-2011:0927 https://rhn.redhat.com/errata/RHSA-2011-0927.html
Comment 7 errata-xmlrpc 2011-08-23 10:42:20 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2011:1189 https://rhn.redhat.com/errata/RHSA-2011-1189.html
Comment 8 errata-xmlrpc 2011-09-12 15:45:15 EDT
This issue has been addressed in following products:

  MRG for RHEL-6 v.2

Via RHSA-2011:1253 https://rhn.redhat.com/errata/RHSA-2011-1253.html

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