On Tue, Apr 25, 2017 at 4:26 AM, PaX Team <pageexec@xxxxxxxxxxx> wrote: > INT_MAX threads would be needed when the leaking path is locked so > that it can only be exercised once and you'll need to get normal > (balanced) paths preempted just after the increment. if the leaking > path is lockless (can be exercised in parallel without bounds) then > 2 threads are enough where the one triggering the signed overflow > would have to be preempted while the other one does INT_MAX increments > and trigger the UAF. this is where the other mechanisms i talked about > in the past become relevant: preemption or interrupts can be disabled > or negative refcount values can be detected and acted upon (your blind > copy-pasting effort passed upon this latter opportunity by not > specializing the 'jo' into 'js' for the refcount case). Well, it's not "blind" -- I'm trying to bring the code as-is to upstream for discussion/examination with as little functional differences as possible so it's easier to compare apples to apples. (Which already resulted in more eyes looking at the code to find a bug -- thanks Jann!) But yes, jo -> js hugely increases the coverage. I'll make that change for v2. Thanks! -Kees -- Kees Cook Pixel Security
