On Thu, Aug 13, 2020 at 06:19:20PM +0300, Alexander Popov wrote: > I've found an easy way to break heap spraying for use-after-free > exploitation. I simply extracted slab freelist quarantine from KASAN > functionality and called it CONFIG_SLAB_QUARANTINE. Please see patch 1. Ah yeah, good idea. :) > [...] > I did a brief performance evaluation of this feature. > > 1. Memory consumption. KASAN quarantine uses 1/32 of the memory. > CONFIG_SLAB_QUARANTINE disabled: > # free -m > total used free shared buff/cache available > Mem: 1987 39 1862 10 86 1907 > Swap: 0 0 0 > CONFIG_SLAB_QUARANTINE enabled: > # free -m > total used free shared buff/cache available > Mem: 1987 140 1760 10 87 1805 > Swap: 0 0 0 1/32 of memory doesn't seem too bad for someone interested in this defense. > 2. Performance penalty. I used `hackbench -s 256 -l 200 -g 15 -f 25 -P`. > CONFIG_SLAB_QUARANTINE disabled (x86_64, CONFIG_SLUB): > Times: 3.088, 3.103, 3.068, 3.103, 3.107 > Mean: 3.0938 > Standard deviation: 0.0144 > CONFIG_SLAB_QUARANTINE enabled (x86_64, CONFIG_SLUB): > Times: 3.303, 3.329, 3.356, 3.314, 3.292 > Mean: 3.3188 (+7.3%) > Standard deviation: 0.0223 That's rather painful, but hackbench can produce some big deltas given it can be an unrealistic workload for most systems. I'd be curious to see the "building a kernel" timings, which tends to be much more realistic for "busy system" without hammering one particular subsystem (though it's a bit VFS heavy, obviously). More notes in the patches... -- Kees Cook
