RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Bug 679262 - [RFE] kernel: kptr_restrict for hiding kernel pointers from unprivileged users [rhel-6.2]
Summary: [RFE] kernel: kptr_restrict for hiding kernel pointers from unprivileged user...
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.2
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: rc
: ---
Assignee: Phillip Lougher
QA Contact: Boris Ranto
URL:
Whiteboard:
Depends On: 679261 679263
Blocks: 1300182
TreeView+ depends on / blocked
 
Reported: 2011-02-22 04:40 UTC by Eugene Teo (Security Response)
Modified: 2016-01-20 08:09 UTC (History)
12 users (show)

Fixed In Version: kernel-2.6.32-150.el6
Doc Type: Enhancement
Doc Text:
In Red Hat Enterprise Linux 6.2, due to security concerns, addresses in /proc/kallsyms and /proc/modules show all zeros when accessed by a non-root user.
Clone Of: 679261
Environment:
Last Closed: 2011-12-06 12:43:58 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:1530 0 normal SHIPPED_LIVE Moderate: Red Hat Enterprise Linux 6 kernel security, bug fix and enhancement update 2011-12-06 01:45:35 UTC

Description Eugene Teo (Security Response) 2011-02-22 04:40:52 UTC 
+++ This bug was initially created as a clone of Bug #679261 +++

Description of problem:
Add the %pK printk format specifier and the /proc/sys/kernel/kptr_restrict sysctl.
    
The %pK format specifier is designed to hide exposed kernel pointers, specifically via /proc interfaces.  Exposing these pointers provides an easy target for kernel write vulnerabilities, since they reveal the locations of writable structures containing easily triggerable function pointers.  The behavior of %pK depends on the kptr_restrict sysctl.
    
If kptr_restrict is set to 0, no deviation from the standard %p behavior occurs.  If kptr_restrict is set to 1, the default, if the current user (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG (currently in the LSM tree), kernel pointers using %pK are printed as 0's. If kptr_restrict is set to 2, kernel pointers using %pK are printed as 0's regardless of privileges.  Replacing with 0's was chosen over the default "(null)", which cannot be parsed by userland %p, which expects "(nil)".

Upstream commit:
http://git.kernel.org/linus/455cd5ab305c90ffc422dd2e0fb634730942b257

Also backport:
drm: do not leak kernel addresses via /proc/dri/*/vma
http://git.kernel.org/linus/01e2f533a234dc62d16c0d3d4fb9d71cf1ce50c3

timer debug: Hide kernel addresses via %pK in /proc/timer_list
http://git.kernel.org/linus/f590308536db432e4747f562b29e5858123938e9

[PATCH v2] use %pK for /proc/kallsyms and /proc/modules
http://marc.info/?l=linux-kernel&m=129608894604282&w=2 (not upstream yet)
Comment 1 Phillip Lougher 2011-04-04 17:23:18 UTC 
(In reply to comment #0)

> [PATCH v2] use %pK for /proc/kallsyms and /proc/modules
> http://marc.info/?l=linux-kernel&m=129608894604282&w=2 (not upstream yet)

Now in mainline

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=9f36e2c448007b54851e7e4fa48da97d1477a175
Comment 2 Phillip Lougher 2011-04-12 15:25:48 UTC 
(In reply to comment #0)

> If kptr_restrict is set to 0, no deviation from the standard %p behavior
> occurs.  If kptr_restrict is set to 1, the default, if the current user
> (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG
> (currently in the LSM tree), kernel pointers using %pK are printed as 0's.
>
> Upstream commit:
> http://git.kernel.org/linus/455cd5ab305c90ffc422dd2e0fb634730942b257
>

This patch requires the CAP_SYSLOG capability, added by mainline commit

http://git.kernel.org/linus/ce6ada35bdf710d16582cc4869c26722547e6f11 

options?

1. Replace CAP_SYSLOG with CAP_SYS_ADMIN
2. Add CAP_SYSLOG patch
3. reject BZ
Comment 3 Eugene Teo (Security Response) 2011-04-13 02:07:53 UTC 
(In reply to comment #2)
> (In reply to comment #0)
> 
> > If kptr_restrict is set to 0, no deviation from the standard %p behavior
> > occurs.  If kptr_restrict is set to 1, the default, if the current user
> > (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG
> > (currently in the LSM tree), kernel pointers using %pK are printed as 0's.
> >
> > Upstream commit:
> > http://git.kernel.org/linus/455cd5ab305c90ffc422dd2e0fb634730942b257
> >
> 
> This patch requires the CAP_SYSLOG capability, added by mainline commit
> 
> http://git.kernel.org/linus/ce6ada35bdf710d16582cc4869c26722547e6f11 
> 
> options?
> 
> 1. Replace CAP_SYSLOG with CAP_SYS_ADMIN
> 2. Add CAP_SYSLOG patch
> 3. reject BZ

Perhaps take option 1, and then mention about the CAP_SYSLOG patch in your patch submission for discussion.
Comment 4 Aristeu Rozanski 2011-05-18 20:07:57 UTC 
Patch(es) available on kernel-2.6.32-150.el6
Comment 15 Martin Prpič 2011-11-22 09:57:56 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
In Red Hat Enterprise Linux 6.2, due to security concerns, addresses in /proc/kallsyms and /proc/modules show all zeros when accessed by a non-root user.
Comment 16 errata-xmlrpc 2011-12-06 12:43:58 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1530.html
Note You need to log in before you can comment on or make changes to this bug.