hw: cpu: LFENCE/JMP Mitigation Update for CVE-2017-5715

LFENCE/JMP (mitigation V2-2) may not sufficiently mitigate CVE-2017-5715 on some AMD CPUs.

Improper validation of the BIOS directory may allow for searches to read beyond the directory table copy in RAM, exposing out of bounds memory contents, resulting in a potential denial of service.

A malicious or compromised UApp or ABL may be used by an attacker to issue a malformed system call to the Stage 2 Bootloader potentially leading to corrupt memory and code execution.

A malformed SMI (System Management Interface) command may allow an attacker to establish a corrupted SMI Trigger Info data structure, potentially leading to out-of-bounds memory reads and writes when triggering an SMI resulting in a potential loss of resources.

An attacker with root account privileges can load any legitimately signed firmware image into the Audio Co-Processor (ACP,) irrespective of the respective signing key being declared as usable for authenticating an ACP firmware image, potentially resulting in a denial of service.

A malicious or compromised UApp or ABL may be used by an attacker to send a malformed system call to the bootloader, resulting in out-of-bounds memory accesses.

Insufficient check of the process type in Trusted OS (TOS) may allow an attacker with privileges to enable a lesser privileged process to unmap memory owned by a higher privileged process resulting in a denial of service.

An attacker, who gained elevated privileges via some other vulnerability, may be able to read data from Boot ROM resulting in a loss of system integrity.

A malicious or compromised UApp or ABL could potentially change the value that the ASP uses for its reserved DRAM, to one outside of the fenced area, potentially leading to data exposure.

A malicious or compromised UApp or ABL may be used by an attacker to issue a malformed system call which results in mapping sensitive System Management Network (SMN) registers leading to a loss of integrity and availability.

A malicious or compromised User Application (UApp) or AGESA Boot Loader (ABL) could be used by an attacker to exfiltrate arbitrary memory from the ASP stage 2 bootloader potentially leading to information disclosure.

Insufficient DRAM address validation in System Management Unit (SMU) may result in a DMA (Direct Memory Access) read/write from/to invalid DRAM address that could result in denial of service.

hw: cpu: AMD CPUs may transiently execute beyond unconditional direct branch

Some AMD CPUs may transiently execute beyond unconditional direct branches, which may potentially result in data leakage.

A bug in AMD CPU’s core logic may allow for an attacker, using specific code from an unprivileged VM, to trigger a CPU core hang resulting in a potential denial of service. AMD believes the specific code includes a specific x86 instruction sequence that would not be generated by compilers.

Insufficient DRAM address validation in System Management Unit (SMU) may result in a DMA read from invalid DRAM address to SRAM resulting in SMU not servicing further requests.

Insufficient bounds checking in System Management Unit (SMU) may cause invalid memory accesses/updates that could result in SMU hang and subsequent failure to service any further requests from other components.

Failure to verify the protocol in SMM may allow an attacker to control the protocol and modify SPI flash resulting in a potential arbitrary code execution.