Re: OK, so culicidae is *still* broken

On 2017-04-20 16:57:03 +0530, Amit Kapila wrote:
> On Wed, Apr 19, 2017 at 9:01 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2017-04-19 10:15:31 -0400, Tom Lane wrote:
> >> Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:
> >> > On Sun, Apr 16, 2017 at 3:04 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> >> Obviously, any such fix would be a lot more likely to be reliable in
> >> >> 64-bit machines. There's probably not enough daylight to be sure of
> >> >> making it work in 32-bit Windows, so I suspect we'd need some retry
> >> >> logic anyway for that case.
> >>
> >> > Yeah, that kind of thing can work assuming we don't get conflicts too
> >> > often, but it could be possible that conflicts are not reported from
> >> > ASLR enabled environments because of commit 7f3e17b4.
> >>
> >> Right, but Andres' point is that we should make an effort to undo that
> >> hack and instead allow ASLR to happen. Not just because it's allegedly
> >> more secure, but because we may have no choice in future Windows versions.
> >
> > FWIW, I think it *also* might make us more secure, because addresses in
> > the postgres binary won't be predictable anymore.
> >
>
> Agreed. I have done some further study by using VMMap tool in Windows
> and it seems to me that all 64-bit processes use address range
> (0000000000010000 ~ 000007FFFFFE0000). I have attached two screen
> shots to show the address range (lower range and upper range). You
> need to refer the lower half of the window in attached screenshots.
> At this stage, I am not completely sure whether we can assume some
> address out of this range to use in MapViewOfFileEx. Let me know your
> thoughts.

That seems like a fairly restricted range (good!), and squares with
memories of reading about this (can't find the reference anymore). Just
using something like 0x00000F0000000000 as the address might work
sufficiently well. What happens if you just hardcode that in the first
MapViewOfFileEx call, and change RandomizedBaseAddress="FALSE" in
src/tools/msvc/VCBuildProject.pm to true?

Greetings,

Andres Freund