Security Advisory Important: kernel-rt security and bug fix update

Advisory: RHSA-2009:1239-2
Type: Security Advisory
Severity: Important
Issued on: 2009-09-01
Last updated on: 2009-09-01
Affected Products: Red Hat Enterprise MRG v1 for Red Hat Enterprise Linux (version 5)
CVEs ( CVE-2009-2692


Updated kernel-rt packages that fix several security issues and various
bugs are now available for Red Hat Enterprise MRG 1.1.

This update has been rated as having important security impact by the Red
Hat Security Response Team.

[Updated 1st Sep 2009]
This erratum originally stated that these updated kernel packages corrected
the issue CVE-2009-1895. This was a mistake as the kernel packages do not
contain a fix for this issue. CVE-2009-1895 will be addressed in a future

The kernel-rt packages contain the Linux kernel, the core of any Linux
operating system.

These updated packages fix the following security issues:

* Tavis Ormandy and Julien Tinnes of the Google Security Team reported a
flaw in the SOCKOPS_WRAP macro in the Linux kernel. This macro did not
initialize the sendpage operation in the proto_ops structure correctly. A
local, unprivileged user could use this flaw to cause a local denial of
service or escalate their privileges. (CVE-2009-2692, Important)

* it was discovered that, when executing a new process, the clear_child_tid
pointer in the Linux kernel is not cleared. If this pointer points to a
writable portion of the memory of the new program, the kernel could corrupt
four bytes of memory, possibly leading to a local denial of service or
privilege escalation. (CVE-2009-2848, Important)

* a flaw was found in the way the do_sigaltstack() function in the Linux
kernel copies the stack_t structure to user-space. On 64-bit machines, this
flaw could lead to a four-byte information leak. (CVE-2009-2847, Moderate)

This update also fixes the following bugs:

* the gcc flag "-fno-delete-null-pointer-checks" was added to the kernel
build options. This prevents gcc from optimizing out NULL pointer checks
after the first use of a pointer. NULL pointer bugs are often exploited by
attackers, and keeping these checks is considered a safety measure.

* a bug in the locking strategy for the free_pages_bulk() kernel function
was found, where a lock in a code branch was not held. This could have
created a "double free" problem that resulted in a kernel panic.

* udevd and multipathd were unable to service events fast enough when a
Fibre Channel cable was unplugged. This caused the cable state to be out of
sync if the cable was plugged back in quickly, possibly resulting in
devices being removed, or path issues when using Device-Mapper Multipath.
This has been changed so that users can specify devices that should not be
removed if a cable is unplugged. (BZ#514541)

* a race condition in exit_thread() could have eventually caused a kernel
oops. (BZ#514587)

* a race condition was fixed between kthread_stop() and kthread_create().
Kernel subsystems creating and stopping threads at a fast pace could hit
this issue. Several inexplicable backtraces observed during tests
caused this race condition. (BZ#518967)

* HPET_EMULATE_RTC was being disabled during kernel compile. This was
caused by an incorrect requirement in the related Kconfig entry. This issue
led to failures when accessing the RTC (real time clock) in machines that
had the RTC emulated by HPET (High Precision Event Timer). (BZ#519433)

Users should upgrade to these updated packages, which contain backported
patches to correct these issues. The system must be rebooted for this
update to take effect.


Before applying this update, make sure that all previously-released
errata relevant to your system have been applied.

This update is available via Red Hat Network. Details on how to use
the Red Hat Network to apply this update are available at

Updated packages

Red Hat Enterprise MRG v1 for Red Hat Enterprise Linux (version 5)

File outdated by:  RHBA-2013:0927
    MD5: 6df882b3c6ff530778113d37f80c6c36
File outdated by:  RHBA-2013:0927
    MD5: b1b84fc956afe0e8b5a99a6067c702ed
File outdated by:  RHBA-2013:0927
    MD5: 78fef054dbfd68ee1ff26f8592d2f702
File outdated by:  RHBA-2013:0927
    MD5: 2de15122a7de1b6707ef8ed91169c401
File outdated by:  RHBA-2013:0927
    MD5: 7df7f3bef4a2f60db185e91d77a0ca6a
File outdated by:  RHBA-2013:0927
    MD5: 1464e4b244b1b56df6330946a75d3ef5
File outdated by:  RHBA-2013:0927
    MD5: ef68c6d3d0b7ac8ce9407764e420b7e8
File outdated by:  RHBA-2013:0927
    MD5: 223bb9b8e60079157085ef15eed956c9
File outdated by:  RHBA-2013:0927
    MD5: 5c7b2b461cf59842eb28a1096649e72c
File outdated by:  RHBA-2013:0927
    MD5: 3e934e159c2ccb81d48079cfd910b876
File outdated by:  RHBA-2013:0927
    MD5: fbe5b9c17c4b902d260c7ed30b882ced
File outdated by:  RHBA-2013:0927
    MD5: 77d952a832ce057f3a7001b47015561d
File outdated by:  RHBA-2013:0927
    MD5: a09bc421aa7221ac856a35c57bae03f1
File outdated by:  RHBA-2013:0927
    MD5: 27b816cbe2cea5abcafc8dc64fc951a3
File outdated by:  RHBA-2013:0927
    MD5: 1464e4b244b1b56df6330946a75d3ef5
File outdated by:  RHBA-2013:0927
    MD5: cf8d4f73473c4bb5def19f2c875f17a0
File outdated by:  RHBA-2013:0927
    MD5: da34641650e73284fb635967b1da4337
File outdated by:  RHBA-2013:0927
    MD5: a9c2918ab987eba788957fa13d106a2a
File outdated by:  RHBA-2013:0927
    MD5: 77006d694694120ad043d38c1d9ed2b4
(The unlinked packages above are only available from the Red Hat Network)

Bugs fixed (see bugzilla for more information)

511187 - kernel: build with -fno-delete-null-pointer-checks [mrg-1]
514541 - [FOCUS] [MRG-1] When the dev_loss_tmo fires don't remove devices by default.
515392 - CVE-2009-2847 kernel: information leak in sigaltstack
515423 - CVE-2009-2848 kernel: execve: must clear current->clear_child_tid
516949 - CVE-2009-2692 kernel: uninit op in SOCKOPS_WRAP() leads to privesc


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