Red Hat Security Advisory: kernel security and bug fix update

Important

A race condition was found in the Linux kernel before version 4.11-rc1 in 'fs/timerfd.c' file which allows a local user to cause a kernel list corruption or use-after-free via simultaneous operations with a file descriptor which leverage improper 'might_cancel' queuing. An unprivileged local user could use this flaw to cause a denial of service of the system. Due to the nature of the flaw, privilege escalation cannot be fully ruled out, although we believe it is unlikely.

CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

The madvise_willneed function in the Linux kernel allows local users to cause a denial of service (infinite loop) by triggering use of MADVISE_WILLNEED for a DAX mapping.

CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

An infinite loop issue was found in the vhost_net kernel module while handling incoming packets in handle_rx(). The infinite loop could occur if one end sends packets faster than the other end can process them. A guest user, maybe a remote one, could use this flaw to stall the vhost_net kernel thread, resulting in a DoS scenario.

CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

A new software page cache side channel attack scenario was discovered in operating systems that implement the very common 'page cache' caching mechanism. A malicious user/process could use 'in memory' page-cache knowledge to infer access timings to shared memory and gain knowledge which can be used to reduce effectiveness of cryptographic strength by monitoring algorithmic behavior, infer access patterns of memory to determine code paths taken, and exfiltrate data to a blinded attacker through page-granularity access times as a side-channel.

CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor

A use-after-free vulnerability was found in the way the Linux kernel's KVM hypervisor emulates a preemption timer for L2 guests when nested (=1) virtualization is enabled. This high resolution timer(hrtimer) runs when a L2 guest is active. After VM exit, the sync_vmcs12() timer object is stopped. The use-after-free occurs if the timer object is freed before calling sync_vmcs12() routine. A guest user/process could use this flaw to crash the host kernel resulting in a denial of service or, potentially, gain privileged access to a system.

CWE-416 - Use After Free

A flaw was found in the Linux kernel's implementation of IPMI (remote baseband access). An attacker, with local access to read /proc/ioports, may be able to create a use-after-free condition when the kernel module is unloaded which may result in privilege escalation.

CWE-416 - Use After Free