On Tue, Jan 17, 2017 at 07:54:38PM +0100, PaX Team wrote: > On 17 Jan 2017 at 17:48, Mark Rutland wrote: > > That being the case, (and given the relevant bug has now been fixed), > > it's not clear to me what the value of this is today. i.e. given the > > general case, is this preventing many leaks? > > no idea, i stopped looking at the instrumentation log long ago, but everyone > can enable the debug output (has a very specific comment on it ;) and look at > the results. i keep this plugin around because it costs nothing to maintain > it and the alternative (better) solution doesn't exist yet.
Fair enough; understood. > > > i never went into that direction because i think the security goal can > > > be achieved without the performance impact of forced initialization. > > > > Was there a particular technique you had in mind? > > sure, i mentioned it in my SSTIC'12 keynote (page 36): > https://pax.grsecurity.net/docs/PaXTeam-SSTIC12-keynote-20-years-of-PaX.pdf Thanks for the pointer. I'm probably being very naive here, but IIUC the per-task usercopy stack would require roughly the same analysis to identify relevant variables, unless all local variables (regardless of initialisation) that fed into a usercopy would be on the usercopy stack? Regardless, I can see the benefit of cleanly separating that data from the rest of the kernel data. Thanks, Mark.
