Bug 667912 - (CVE-2011-0006) CVE-2011-0006 kernel: ima: fix add LSM rule bug
CVE-2011-0006 kernel: ima: fix add LSM rule bug
Status: CLOSED ERRATA
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
low Severity low
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Assigned To: Red Hat Product Security
public=20110104,reported=20110107,sou...
: Security
Depends On: 667914 667915
Blocks:
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Reported: 2011-01-07 04:09 EST by Eugene Teo (Security Response)
Modified: 2015-08-19 05:02 EDT (History)
8 users (show)

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Doc Type: Bug Fix
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Last Closed: 2015-07-29 09:37:14 EDT
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RHEL 7.3 requirements from Atomic Host:


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Description Eugene Teo (Security Response) 2011-01-07 04:09:53 EST
If security_filter_rule_init() doesn't return a rule, then not everything is as fine as the return code implies.
    
This bug only occurs when the LSM (eg. SELinux) is disabled at runtime.    

Adding an empty LSM rule causes ima_match_rules() to always succeed, ignoring any remaining rules.
    
     default IMA TCB policy:
      # PROC_SUPER_MAGIC
      dont_measure fsmagic=0x9fa0
      # SYSFS_MAGIC
      dont_measure fsmagic=0x62656572
      # DEBUGFS_MAGIC
      dont_measure fsmagic=0x64626720
      # TMPFS_MAGIC
      dont_measure fsmagic=0x01021994
      # SECURITYFS_MAGIC
      dont_measure fsmagic=0x73636673
    
      < LSM specific rule >
      dont_measure obj_type=var_log_t
    
      measure func=BPRM_CHECK
      measure func=FILE_MMAP mask=MAY_EXEC
      measure func=FILE_CHECK mask=MAY_READ uid=0
    
Thus without the patch, with the boot parameters 'tcb selinux=0', adding the above 'dont_measure obj_type=var_log_t' rule to the default IMA TCB measurement policy, would result in nothing being measured.  The patch prevents the default TCB policy from being replaced.

Upstream commit:
http://git.kernel.org/linus/867c20265459d30a01b021a9c1e81fb4c5832aa9

Introduced in 2.6.30-rc1 4af4662f
Comment 2 Eugene Teo (Security Response) 2011-01-11 03:53:13 EST
Statement:

The Linux kernel as shipped with Red Hat Enterprise Linux 4, 5, and Red Hat Enterprise MRG are not affected by this issue. A future kernel update in Red Hat Enterprise Linux 6 may address this flaw.
Comment 4 errata-xmlrpc 2011-05-10 14:11:29 EDT
This issue has been addressed in following products:

  Red Hat Enterprise Linux 6

Via RHSA-2011:0498 https://rhn.redhat.com/errata/RHSA-2011-0498.html

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