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SUMMARY:Baggy bounds checking - Periklis Akritidis (University of Cambridg
 e)
DTSTART:20090127T130000Z
DTEND:20090127T133000Z
UID:TALK16741@talks.cam.ac.uk
CONTACT:Stephen Kell
DESCRIPTION:The adoption of runtime bounds checking for C programs is limi
 ted because it either breaks interoperability by modifying the pointer rep
 resentation to include bounds or incurs significant performance overhead t
 o lookup the bounds in a data structure. We improve this for security purp
 oses by observing that enforcing looser bounds still severely limits attac
 kers\, as long as we pad objects to the new\, baggy bounds thus preventing
  access to any potential target objects. We take advantage of this more fl
 exible integrity guarantee to increase performance by padding and aligning
  allocations to a power of two\, enabling a byte-size representation of th
 e allocation bounds that is efficient to store\, lookup and check. As expe
 cted\, padding incurs space and runtime overheads\, but these turn out to 
 be far less than the gains for bounds checking: our technique is more than
  three times faster---and orthogonal---to the state of the art technique o
 n the same benchmarks\, and an order of magnitude faster\, using less memo
 ry\, compared to using splay trees instead of padding\, sharing the same i
 mplementation for everything else. 
LOCATION:Computer Laboratory\, William Gates Building\, Room FW11
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