ALAS-2019-1165


Amazon Linux AMI Security Advisory: ALAS-2019-1165
Advisory Release Date: 2019-03-04 23:51 Pacific
Severity: Important

Issue Overview:

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. (CVE-2019-7221 )

A use-after-free vulnerability was found in the way the Linux kernel's KVM hypervisor implements its device control API. While creating a device via kvm_ioctl_create_device(), the device holds a reference to a VM object, later this reference is transferred to the caller's file descriptor table. If such file descriptor was to be closed, reference count to the VM object could become zero, potentially leading to a use-after-free issue. A user/process could use this flaw to crash the guest VM resulting in a denial of service issue or, potentially, gain privileged access to a system. (CVE-2019-6974 )

An information leakage issue was found in the way Linux kernel's KVM hypervisor handled page fault exceptions while emulating instructions like VMXON, VMCLEAR, VMPTRLD, and VMWRITE with memory address as an operand. It occurs if the operand is a mmio address, as the returned exception object holds uninitialized stack memory contents. A guest user/process could use this flaw to leak host's stack memory contents to a guest. (CVE-2019-7222 )


Affected Packages:

kernel


Issue Correction:
Run yum update kernel to update your system.

New Packages:
i686:
    kernel-4.14.101-75.76.amzn1.i686
    kernel-tools-devel-4.14.101-75.76.amzn1.i686
    kernel-tools-debuginfo-4.14.101-75.76.amzn1.i686
    kernel-debuginfo-4.14.101-75.76.amzn1.i686
    kernel-headers-4.14.101-75.76.amzn1.i686
    perf-debuginfo-4.14.101-75.76.amzn1.i686
    kernel-tools-4.14.101-75.76.amzn1.i686
    perf-4.14.101-75.76.amzn1.i686
    kernel-debuginfo-common-i686-4.14.101-75.76.amzn1.i686
    kernel-devel-4.14.101-75.76.amzn1.i686

src:
    kernel-4.14.101-75.76.amzn1.src

x86_64:
    kernel-debuginfo-common-x86_64-4.14.101-75.76.amzn1.x86_64
    perf-debuginfo-4.14.101-75.76.amzn1.x86_64
    kernel-tools-debuginfo-4.14.101-75.76.amzn1.x86_64
    kernel-tools-devel-4.14.101-75.76.amzn1.x86_64
    kernel-headers-4.14.101-75.76.amzn1.x86_64
    kernel-debuginfo-4.14.101-75.76.amzn1.x86_64
    kernel-4.14.101-75.76.amzn1.x86_64
    perf-4.14.101-75.76.amzn1.x86_64
    kernel-devel-4.14.101-75.76.amzn1.x86_64
    kernel-tools-4.14.101-75.76.amzn1.x86_64