Rowhammer Flaw-An Unusual DRAM Bug yields Kernel read-write Access.

📅 April 19, 2017 - Rowhammer flaw is Exceptional bug found in DRAM. This exploits complete physical memory of x86-64 Linux machines by contentiously accessing DRAM memory row till it turns into Bit Flips in adjacent rows. This Bug has been found in DDR3 and DDR4 DRAM memory devices. A Malicious Attacker can collect the data like machine password and access the main memory content through vulnerable Storage devices.

How Rowhammer flaw induce Bit Flip?

Rowhammer manipulates DRAM Memory rows and force for repeated reading and recharge the capacitors in DRAM Chip, when attacker use the machine code instruction CLFLUSH to clear the cache. Overload of CLFLUSH process will cause Bit Flipping and infect the neighboring capacitors.

An Organization built two working privileges to test the effects of Rowhammer bug. When The memory rows are accessed by unauthorized user, the bit flips into adjacent rows and gained complete ketnel privileges. When accessed by authorized user the bit flips infected the page table entries of machine vulnerable to Rowhammer problem. Hence an attacker gets Both Read-write access to the physical machine.

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