The Linux kernel's memory allocators from an exploitation perspective [LWN.net]

"Argp" has posted a lengthy look at the kernel's memory allocators and how they can be exploited to attack the system. "The attack vector of corrupting adjacent objects on the same slab is fully applicable to SLUB and largely works like in the case of the SLAB allocator. However, in the case of SLUB there is an added attack vector: exploiting the allocator’s metadata (the ones responsible for finding the next free object on the slab). As twiz and sgrakkyu have demonstrated in their book on kernel exploitation, the slab can be misaligned by corrupting the least significant byte of the metadata of a free object that hold the pointer to the next free object. This misalignment of the slab allows us to create an in-slab fake object and by doing so to a) satisfy safeguard checks as the one I explained in the previous paragraph when they are used, and b) to hijack the kernel’s execution flow to our own code."

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