That makes sense, as you're fucked by any false positive.
If it's a graph of potential stacks, though, wouldn't you eventually find the one that unwinds, if one exists?
GP mentioned in another comment that they don't actually follow the algorithm described by userbinator -- checking the return address for a preceding call -- which would increase the number of false positives a lot.
The thing that makes this tricky is that x86 is a variable length instruction set: you don't know where the preceding call instruction might begin, and you can't decode backwards. You can do it speculatively, but ambiguities are still possible.
Given that the full technique apparently works well for userbinator, we can assume that this isn't a very significant issue. The chances of a phantom call instruction will be pretty low, and there's a fairly low maximum instruction length.
Yes, but checking for valid CALL instructions is probably sufficiently accurate.
Is this just an artifact of old return addresses on the stack not being overwritten?