GPUHammer: Rowhammer attacks on GPU memories are practical
55 comments
·July 16, 2025PeterStuer
lukan
"I always found hammering attacks to be extremely satisfying"
On a philosophical level I somewhat agree, but on a practical level I am sad as this likely means reduced performance again.
arduinomancer
I tried knocking on my wall 100,000 times and it did indeed cause a disturbance in the neighbouring cell of my apartment
Turns out this whole virtualized house abstraction is a sham
SandmanDP
> Makes you dream there could be an equivalent for our own universe?
I’ve always considered that to be what’s achieved by the LHC: smashing the fundamental building blocks of our universe together at extreme enough energies to briefly cause ripples through the substrate of said universe
simiones
The LHC doesn't generate anything like the kind of energy that you get when interstellar particles hit the Earth's upper atmosphere, nevermind what's happening inside the sun - and any of these are many, many orders of magnitude below the energies you get in a supernova, for example.
The LHC is extremely impressive from a human engineering perspective, but it's nowhere close to pushing the boundaries of what's going on every second in the universe at large.
whyowhy3484939
That's assuming there is a substrate that can be disturbed. That's where the parent's analogy breaks down.
As an example of an alternative analogy: think of how many bombs need to explode in your dreams before the "substrate" is "rippled". How big do the bombs need to be? How fast does the "matter" have to "move"? I think "reality" is more along those lines. If there is a substrate - and that's a big if - IMO it's more likely to be something pliable like "consciousness". Not in the least "disturbed" by anything moving in it.
hoseja
Well for Earth life there are multiple but evolution just learned to exploit them all.
userbinator
No one really cared about the occasional bitflips in VRAM when GPUs were only used for rendering graphics. It's odd that enabling ECC can reduce performance, unless they mean that's only in the presence of ECC errors being corrected, since AFAIK for CPUs there isn't any difference in speed even when correcting errors.
In a proof-of-concept, we use these bit flips to tamper with a victim’s DNN models and degrade model accuracy from 80% to 0.1%, using a single bit flip
There is a certain irony in doing this to probabilistic models, designed to mimic an inherently error-prone and imprecise reality.
ryao
Nvidia implements ECC in software since they did not want to add the extra memory chip(s) needed to implement it in hardware to their boards. The only case where they do it in hardware is when they use HBM memory.
That said, GDDR7 does on die ECC, which gives immunity to this in its current form. There is no way to get information on corrected bitflips from on-die ECC, but it is better than nothing.
hamandcheese
Available ECC dims are often slower than non-ECC dims. Both slower MT/s and higher latency. At least for "prosumer" ECC UDIMMs which are what I'm familiar with.
So it doesn't seem that wild to me that turning on ECC might require running at lower bandwidth.
ryao
This is incorrect. ECC DIMMs are no slower than regular DIMMs. Instead, they have extra memory and extra memory bandwidth. A 8GB DDR4 ECC DIMM would have 9GB of memory and 9/8 the memory bandwidth. The extra memory is used to store the ECC bits while the extra memory bandwidth is to prevent performance loss when reading/writing ECC alongside the rest of the memory. The memory controller will spend an extra cycle verifying the ECC, which is a negligible performance hit. In reality, there is no noticeable performance difference. However, where you would have 128 traces to a Zen 3 CPU for DDR4 without ECC, you would need 144 traces for DDR4 with ECC.
A similar situation occurs with GDDR6, except Nvidia was too cheap to implement the extra traces and pay for the extra chip, so instead, they emulate ECC using the existing memory and memory bandwidth, rather than adding more memory and memory bandwidth like CPU vendors do. This causes the performance hit when you turn on ECC on most Nvidia cards. The only exception should be the HBM cards, where the HBM includes ECC in the same way it is done on CPU memory, so there should be no real performance difference.
bilegeek
Their second point is wrong (unless the silicon is buggy), but their first point is true. I researched when buying ECC sticks for my rig; nobody that I've found makes unregistered sticks that go above 5600, while some non-ECC sticks are already at 8200, and 6400 is commonplace.
Frustratingly, it's only unregistered that's stuck in limbo; VCC makes a kit of registered 7200.
null
privatelypublic
This seems predicated on there being significant workloads that split gpu's between tenants for compute purposes.
Anybody have sizable examples? Everything I can think of results in dedicated gpus.
vlovich123
Many of the GPU rental companies charge less for shared GPU workloads. So it's a cost/compute tradeoff. It's usually not about the workload itself needing the full GPU unless you really need all the RAM on a single instance.
privatelypublic
Any examples to check out? The only one i know of is vastai... and there's already a list of security issues a mile long there.
huntaub
My (limited) understanding was that the industry previously knew that it was unsafe to share GPUs between tenants, which is why the major cloud providers only sell dedicated GPUs.
bluedino
NVIDIA GPU's can run in MIG (Multi-Instance GPU), allowing you to pack more jobs on than you have GPUs. Very common in HPC but I don't about in the cloud.
privatelypublic
I thought about splitting the GPU between workloads, as well terminal server/virtualized desktop situations.
I'd expect all code to be strongly controlled in the former, and reasonably secured in the latter with software/driver level mitigations possible and the fact that corrupting somebody else's desktop with row-hammer doesn't seem like good investment.
As another person mentioned- and maybe it is a wider usage than I thought- cloud gpu compute running custom code seems to be the only useful item. But, I'm having a hard time coming up with a useful scenario. Maybe corrupting a SIEM's analysis & alerting of an ongoing attack?
cyberax
No large cloud hoster (AWS, Google, Azure) shares GPUs between tenants.
privatelypublic
Update: I thought for a second I had one: Jupyter notebook services with GPUs- but looking at google colab^* even there its a dedicated GPU for that session.
* random aside: how is colab compute credits having a 90 day expiration legal? I thought california outlawed company-currency expiring? (A la gift cards)
dogma1138
Colab credits aren’t likely a currency equivalent but a service equivalent which is still legal to expire afaik.
Basically Google Colab credits is like buying a seasonal bus pass with X trips or a monthly parking pass with X amount of hours. Rather than getting store cash which can be used for anything.
SnowflakeOnIce
Example: A workstation or consumer GPU used both for rendering the desktop and running some GPGPU thing (like a deep neural network)
privatelypublic
Not an issue- thats a single Tennant.
Which is my point.
spockz
Until the GPU is accessible by the browser and any website can execute code on it. Or the attack can come from a different piece of software on your machine.
haiku2077
GKE can share a single GPU between multiple containers in a partitioned or timeshared scheme: https://cloud.google.com/kubernetes-engine/docs/concepts/tim...
privatelypublic
Thats the thing... they're all the same tennant. A GKE node is a VM instance, and GCE doesn't have shared GPUs that I can see.
null
im3w1l
Webgpu api taking screenshot of full desktop maybe?
privatelypublic
Rowhammer itself is a write-only attack vector. It can, however, potentially be chained to change the write address to an incorrect region. Haven't dived into details.
SnowflakeOnIce
How is it a write-only attack vector?
Buttons840
Do you think WebGPU would be any more of an attack vector than WebGL?
perching_aix
HW noob here, anyone here has insight on how an issue like this passes EM simulation during development? I understand that modern chips are way too complex for full formal verification, but I'd have thought memory modules would be so highly structurally regular that it might be possible there despite it.
andyferris
I am no expert in the field, but my reading of the original rowhammer issue (and later partial hardware mitigations) was that it was seen as better to design RAM that works fast and is dense and get that to market, than to engineer something provably untamperable with greater tolerances / die size / latency.
GPUs have always been squarely in the "get stuff to consumers ASAP" camp, rather than NASA-like engineering that can withstand cosmic rays and such.
I also presume an EM simulation would be able to spot it, but prior to rowhammer it is also possible no-one ever thought to check for it (or more likely that they'd check the simulation with random or typical data inputs, not a hitherto-unthought-of attack vector, but that doesn't explain more modern hardware).
privatelypublic
I seem to recall that rowhammer was known- but thought impossible for userland code to implement.
This is a huge theme for vulnerabilities. I almost said "modern" but looking back I've seen the cycle (disregard attacks as strictly hypothetical. Get caught unprepared when somebody publishes something making it practical) happen more than a few times.
Palomides
someone did a javascript rowhammer in 2015, hardware that's vulnerable today is just manufacturers and customers deciding they don't want to pay for mitigation
(personally I think all RAM in all devices should be ECC)
userbinator
but prior to rowhammer it is also possible no-one ever thought to check for it
It was known as "pattern sensitivity" in the industry for decades, basically ever since the beginning, and considered a blocking defect. Here's a random article from 1989 (don't know why first page is missing, but look at the references): http://web.eecs.umich.edu/~mazum/PAPERS-MAZUM/patternsensiti...
Then some bastards like these came along...
https://research.ece.cmu.edu/safari/thesis/skhan_jobtalk_sli...
...and essentially said "who cares, let someone else be responsible for the imperfections while we can sell more crap", leading to the current mess we're in.
The flash memory industry took a similar dark turn decades ago.
MadnessASAP
Given that I wasnt surprised by the headlie Inhave to imagine that nvidia engineers were also well aware.
Nothing is perfect, everything has its failure conditions. The question is where do you choose to place the bar? Do you want your component to work at 60, 80, or 100C? Do you want it to work in high radiation environments? Do you want it to withstand pathological access patterns?
So in other words, there isnt a sufficent market for GPUs at double the $/GB RAM but are resilient to rowhammer attacks to justify manufacturing them.
thijsr
Rowhammer is an inherent problem to the way we design DRAM. It is a known problem to memory manufacturers that is very hard, if not impossible, to fix. In fact, Rowhammer only becomes worse as the memory density increases.
sroussey
It’s a matter of percentages… not all manufacturers fell to the rowhammer attack.
The positive part of the original rowhammer report was that it gave us a new tool to validate memory (it caused failures much faster than other validation methods).
iFire
Does the ECC mode on my 4090 Nvidia rtx stop this?
fc417fc802
Yes, but it reduces performance, and you don't need to care about this because (presumably) you aren't a cloud provider running multi-tenant workloads.
Worst case scenario someone pulls this off using webgl and a website is able to corrupt your VRAM. They can't actually steal anything in that scenario (AFAIK) making it nothing more than a minor inconvenience.
I always found hammering attacks to be extremely satisfying, even from a meta-physical pov.
You escape a closed virtual universe by not "breaking out" in the tradidional sense, exploiting some bug in the VM hypervisor's boundary itself, but by directly manipulating the underlying physics of the universe on wich the virtual universe is founded, just by creating a pattern inside the virtual universe itself.
No matter how many virtual digital layers, as long as you can impact the underlying analog substrate this might work.
Makes you dream there could be an equivalent for our own universe?