Recent informative ML thread: List of security features in musl. http://www.openwall.com/lists/musl/2016/02/11/4 …
@CopperheadSec How so? Check header==(footer^secret). This will, with high probability, catch invalid frees.
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@RichFelker Not at all the same. Uninitialized data access and out-of-bounds reads (especially one element past the end) are very common. -
@RichFelker It's not the only missing guarantee anyway. It's just one example a nice security property gained from non-inline metadata. -
@RichFelker Anyway, if you have headers and/or footers, it's not comparable to modern performance-oriented allocators without that overhead. -
@CopperheadSec I'm generally of the view that "modern performance-oriented allocators" are a load of crap. :-) -
@CopperheadSec Headers/footers, if validated well, also go a long way towards mitigating exploitable off-by-1 heap overflows. -
@RichFelker They are, but it can be better without the metadata there at all. Spending two extra bits per allocation isn't very significant. -
@CopperheadSec I've considered size-segregated pools with atomic TAS bitmaps to solve frag, overhead, and lock contention.
End of conversation
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