Fedoraproject

An issue was discovered in Xen through 4.14.x. There are evtchn_reset() race conditions. Uses of EVTCHNOP_reset (potentially by a guest on itself) or XEN_DOMCTL_soft_reset (by itself covered by XSA-77) can lead to the violation of various internal assumptions. This may lead to out of bounds memory accesses or triggering of bug checks. In particular, x86 PV guests may be able to elevate their privilege to that of the host. Host and guest crashes are also possible, leading to a Denial of Service (DoS). Information leaks cannot be ruled out. All Xen versions from 4.5 onwards are vulnerable. Xen versions 4.4 and earlier are not vulnerable.Show less

An issue was discovered in Xen 4.14.x. There is a missing unlock in the XENMEM_acquire_resource error path. The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar to forgetting to unlock a spinlock. A buggy or malicious HVM stubdomain can cause an RCU reference to be leaked. This causes subsequent administration operations, (e.g., CPU offline) to livelock, resulting in a host Denial of Service. The buggy codepath has been present since Xen 4.12. Xen 4.14 and later are vulnerable to the DoS. The side effects are believed to be benign on Xen 4.12 and 4.13, but patches are provided nevertheless. The vulnerability can generally only be exploited by x86 HVM VMs, as these are generally the only type of VM that have a Qemu stubdomain. x86 PV and PVH domains, as well as ARM VMs, typically don't use a stubdomain. Only VMs using HVM stubdomains can exploit the vulnerability. VMs using PV stubdomains, or with emulators running in dom0, cannot exploit the vulnerability.Show less

An issue was discovered in Xen through 4.14.x. There is mishandling of the constraint that once-valid event channels may not turn invalid. Logic in the handling of event channel operations in Xen assumes that an event channel, once valid, will not become invalid over the life time of a guest. However, operations like the resetting of all event channels may involve decreasing one of the bounds checked when determining validity. This may lead to bug checks triggering, crashing the host. An unprivileged guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only systems with untrusted guests permitted to create more than the default number of event channels are vulnerable. This number depends on the architecture and type of guest. For 32-bit x86 PV guests, this is 1023; for 64-bit x86 PV guests, and for all ARM guests, this number is 4095. Systems where untrusted guests are limited to fewer than this number are not vulnerable. Note that xl and libxl limit max_event_channels to 1023 by default, so systems using exclusively xl, libvirt+libxl, or their own toolstack based on libxl, and not explicitly setting max_event_channels, are not vulnerable.Show less

An issue was discovered in Xen through 4.14.x. x86 PV guest kernels can experience denial of service via SYSENTER. The SYSENTER instruction leaves various state sanitization activities to software. One of Xen's sanitization paths injects a #GP fault, and incorrectly delivers it twice to the guest. This causes the guest kernel to observe a kernel-privilege #GP fault (typically fatal) rather than a user-privilege #GP fault (usually converted into SIGSEGV/etc.). Malicious or buggy userspace can crash the guest kernel, resulting in a VM Denial of Service. All versions of Xen from 3.2 onwards are vulnerable. Only x86 systems are vulnerable. ARM platforms are not vulnerable. Only x86 systems that support the SYSENTER instruction in 64bit mode are vulnerable. This is believed to be Intel, Centaur, and Shanghai CPUs. AMD and Hygon CPUs are not believed to be vulnerable. Only x86 PV guests can exploit the vulnerability. x86 PVH / HVM guests cannot exploit the vulnerability.Show less

An issue was discovered in Xen through 4.14.x. The PCI passthrough code improperly uses register data. Code paths in Xen's MSI handling have been identified that act on unsanitized values read back from device hardware registers. While devices strictly compliant with PCI specifications shouldn't be able to affect these registers, experience shows that it's very common for devices to have out-of-spec "backdoor" operations that can affect the result of these reads. A not fully trusted guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. Privilege escalation and information leaks cannot be excluded. All versions of Xen supporting PCI passthrough are affected. Only x86 systems are vulnerable. Arm systems are not vulnerable. Only guests with passed through PCI devices may be able to leverage the vulnerability. Only systems passing through devices with out-of-spec ("backdoor") functionality can cause issues. Experience shows that such out-of-spec functionality is common; unless you have reason to believe that your device does not have such functionality, it's better to assume that it does.Show less

An information disclosure vulnerability was found in containers/podman in versions before 2.0.5. When using the deprecated Varlink API or the Docker-compatible REST API, if multiple containers are created in a short duration, the environment variables from the first container will get leaked into subsequent containers. An attacker who has control over the subsequent containers could use this flaw to gain access to sensitive information stored in such variables.Show less