Saturday, April 20, 2024

AMD Zen 3 & Zen 2 CPUs Vulnerable to Memory Leakage

AMD Zen 3 CPUs

According to recent study from ETH Zurich, AMD’s Zen technology is susceptible to Rowhammer attacks, which could negatively impact DRAM use.

Due to the Zenhammer vulnerability, the AMD advises users to proceed with caution while using relatively older systems with AMD Zen 3 and AMD Zen 2 CPUs.

A very ancient vulnerability called Rowhammer was first discovered in 2014 as a result of collaborative research between Carnegie Mellon University and Intel. The contents of your DRAM are impacted by this breach because it may cause an electric leak in memory cells, which could flip bits and destroy the data stored there. Additionally, it may allow hackers to obtain confidential data; as a result, it is also referred to as “Zenhammer” since it now affects AMD’s Zen systems.

By flipping the bits in the DDR4 memory installed in AMD Zen 2 and AMD Zen 3 computers, independent researchers from ETH Zurich have discovered a method to interfere with the contents of your memory using the Rowhammer implementation. This is how they managed to pull it off:

In order to increase activation throughput while maintaining the access order required to get around in-DRAM mitigations, ZenHammer carefully schedules flush and fence instructions within a pattern, employs specially designed access patterns for proper synchronization, and reverse engineers the DRAM addressing functions despite their non-linear nature.

AMD Zen 2 CPUs

After successfully exploiting the secret DRAM address functions, the researchers were able to modify the timing routine and, through extensive testing, were able to integrate Rowhammer’s effects into the systems, flipping the data stored in the AMD Zen 2 and AMD Zen 3 systems’ memory. The research demonstrations that AMD systems were vulnerable, much like Intel-based systems are. Even while this is concerning for AMD users who are relatively elderly, Team Red has addressed the issue and produced a security brief promptly. AMD is still evaluating the researchers’ assertion that they have successfully demonstrated Rowhammer bit flips on a DDR5 chip. When AMD has finished evaluating the situation, it will release an update.

Memory controllers made by AMD microprocessor products are made to adhere to DDR criteria that are accepted in the industry. Rowhammer attack susceptibility varies according to the type of DRAM device, vendor, technology, and configuration of the system. AMD advises getting in touch with the maker of your DRAM or system to find out if you’re susceptible to this new Rowhammer variation.

Additionally, AMD still suggests the following DRAM defenses against attacks akin to Rowhammer:

  • Utilizing Error Correcting Codes (ECC) supported by DRAM
  • Using memory refresh rates more than 1x
  • Disabling Memory Burst/Postponed Refresh
  • Utilizing memory controllers for AMD CPUs that enable a Maximum Activate Count (MAC) (DDR4)
    • AMD EPYC First Generation Processors, formerly known as “Naples”
    • AMD EPYC 2nd Generation Processors, formerly known as “Rome”
    • AMD EPYC 3rd Generation Processors, formerly known as “Milan”
  • Utilizing memory controllers for AMD CPUs that provide refresh management (RFM) (DDR5)

They advise users who are especially worried about Zenhammer to apply the mitigations that Team Red has recommended in order to protect themselves from the vulnerability. The business is evaluating the circumstances and preparing a more thorough update in the interim.

AMD Zen 3 and AMD Zen 2 CPU Specifications

FeatureAMD Zen 3AMD Zen 2
MicroarchitectureZen 3Zen 2
Manufacturing Process7nm TSMC (chiplets), 12nm or 14nm GlobalFoundries (I/O die)7nm TSMC
Core Complex Configuration1 CCD per chip, 8 cores per CCD, 32 MB L3 cache per CCD1 or 2 CCDs per chip, 4 cores per CCX (Cluster Complex), 16 MB L3 cache per CCX
Supported Instruction SetsAVX2, AVX-512, FMA4AVX2, FMA3
Maximum Core Count1616
Maximum Thread Count3232
Base Clock Speed (GHz)3.3 – 3.73.6 – 4.6
Maximum Boost Clock Speed (GHz)4.6 – 4.94.4 – 4.9
Integrated GraphicsNo (desktop)Yes (some mobile models)


What is the AMD Zen 2 processor?

The upcoming generation of AMD desktop and server processors are powered by Zen 2. In comparison to its predecessor, it has up to twice as many commands per unit of energy. The products were created as chiplet-based solutions that balanced power and cost and allowed for effective technology targeting.

 What is the next generation AMD EPYC?

The 16-chiplet version will have 512MB of L3 cache, while the Zen 5c chip with 12 chiplets will have 384MB. This is because the next generation Epyc CCDs have 32MB of L3 memory.

What is the difference between gen 1 and gen 2 EPYC?

Whereas the second and third generation of EPYC CPUs featured 128 PCIe 4.0 lanes, the first generation’s had 128 PCIe 3.0 lanes. Up to eight DDR4 channels at different speeds are present in all existing EPYC CPUs; however, AMD has indicated that next-generation Genoa CPUs would enable up to twelve DDR5 channels.

News Source

Agarapu Ramesh was founder of the Govindhtech and Computer Hardware enthusiast. He interested in writing Technews articles. Working as an Editor of Govindhtech for one Year and previously working as a Computer Assembling Technician in G Traders from 2018 in India. His Education Qualification MSc.


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