Category Archives: Rowhammer

Peering Into a Running Brain: SDRAM Refresh Analyzed from Userspace

Over on the Cloudflare blog, [Marek] found himself wondering about computer memory, as we all sometimes do. Specifically, he pondered if he could detect the refresh of his SDRAM from within a running program. We’re probably not ruining the surprise by telling you that the answer is yes — with a little more than 100 lines of C and help from our old friend the Fast Fourier Transform (FFT), [Marek] was able to detect SDRAM refresh cycles every 7818.6 ns, lining right up with the expected result.

The “D” in SDRAM stands for dynamic, meaning that unless periodically refreshed by …read more

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Posted in computer hacks, fft, Meltdown, refresh, Rowhammer, sdram, security hacks, Spectre | Leave a comment

33C3: Memory Deduplication, the Hacker’s Friend

At the 33rd annual Chaos Communications Congress, [Antonio Barresi] and [Erik Bosman] presented not one, not two, but three (3!!) great hacks that were all based on exploiting memory de-duplication in virtual machines. If you’re interested in security, you should definitely watch the talk, embedded below. And grab the slides too. (PDF)

Memory de-duplication is the forbidden fruit for large VM setups — obviously dangerous but so tempting. Imagine that you’re hosting VMs and you notice that many of the machines have the same things in memory at the same time. Maybe we’re all watching the same cat videos. They …read more

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Posted in memory, Rowhammer, security hacks | Leave a comment