RHEL 6 : kernel (RHSA-2011:1849)
Medium Nessus Plugin ID 57391
SynopsisThe remote Red Hat host is missing one or more security updates.
DescriptionUpdated kernel packages that fix one security issue and various bugs are now available for Red Hat Enterprise Linux 6.
The Red Hat Security Response Team has rated this update as having important security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.
The kernel packages contain the Linux kernel, the core of any Linux operating system.
Security fix :
* Using the SG_IO IOCTL to issue SCSI requests to partitions or LVM volumes resulted in the requests being passed to the underlying block device. If a privileged user only had access to a single partition or LVM volume, they could use this flaw to bypass those restrictions and gain read and write access (and be able to issue other SCSI commands) to the entire block device.
In KVM (Kernel-based Virtual Machine) environments using raw format virtio disks backed by a partition or LVM volume, a privileged guest user could bypass intended restrictions and issue read and write requests (and other SCSI commands) on the host, and possibly access the data of other guests that reside on the same underlying block device. Partition-based and LVM-based storage pools are not used by default. Refer to Red Hat Bugzilla bug 752375 for further details and a mitigation script for users who cannot apply this update immediately. (CVE-2011-4127, Important)
Bug fixes :
* Previously, idle load balancer kick requests from other CPUs could be serviced without first receiving an inter-processor interrupt (IPI). This could have led to a deadlock. (BZ#750459)
* This update fixes a performance regression that may have caused processes (including KVM guests) to hang for a number of seconds.
* When md_raid1_unplug_device() was called while holding a spinlock, under certain device failure conditions, it was possible for the lock to be requested again, deeper in the call chain, causing a deadlock.
Now, md_raid1_unplug_device() is no longer called while holding a spinlock. (BZ#755545)
* In hpet_next_event(), an interrupt could have occurred between the read and write of the HPET (High Performance Event Timer) and the value of HPET_COUNTER was then beyond that being written to the comparator (HPET_Tn_CMP). Consequently, the timers were overdue for up to several minutes. Now, a comparison is performed between the value of the counter and the comparator in the HPET code. If the counter is beyond the comparator, the '-ETIME' error code is returned.
* Index allocation in the virtio-blk module was based on a monotonically increasing variable 'index'. Consequently, released indexes were not reused and after a period of time, no new were available. Now, virtio-blk uses the ida API to allocate indexes.
* A bug related to Context Caching existed in the Intel IOMMU support module. On some newer Intel systems, the Context Cache mode has changed from previous hardware versions, potentially exposing a Context coherency race. The bug was exposed when performing a series of hot plug and unplug operations of a Virtual Function network device which was immediately configured into the network stack, i.e., successfully performed dynamic host configuration protocol (DHCP).
When the coherency race occurred, the assigned device would not work properly in the guest virtual machine. With this update, the Context coherency is corrected and the race and potentially resulting device assignment failure no longer occurs. (BZ#757671)
* The align_va_addr kernel parameter was ignored if secondary CPUs were initialized. This happened because the parameter settings were overridden during the initialization of secondary CPUs. Also, the align_va_addr parameter documentation contained incorrect parameter arguments. With this update, the underlying code has been modified to prevent the overriding and the documentation has been updated. This update also removes the unused code introduced by the patch for BZ#739456. (BZ#758028)
* Dell systems based on a future Intel processor with graphics acceleration required the selection of the install system with basic video driver installation option. This update removes this requirement. (BZ#758513)
SolutionUpdate the affected packages.