Re: [PATCH 0/5] VA allocator fixes

[Florian Weimer <fweimer@redhat.com>]

On 11/06/2017 11:03 AM, Nicholas Piggin wrote:
> Florian found a nasty corner case with the VA allocation logic
> for crossing from 128TB to 512TB limit on hash, and made a
> really superb report of the problem -- traces, reproducer recipes,
> analysis, etc. which already mostly solved it.
> 
> The first patch in the series should solve Florian's particular
> case, the next 3 are other issues with addr_limit. The last
> patch is technically a cleanup but I think it's fairly important
> in terms of understanding the code and also enabling some BUG
> checks (when addr_limit == 0).
> 
> I have not tested these exactly on Florian's test case, but
> some tests of my own behave better afterwards. Hopefully he has
> time to re-test. Some careful review would be welcome too.

I think I have applied the five patches you posted, but I still get a 
brk value above 128 TiB:

# /lib64/ld64.so.1 ./a.out
initial brk value: 0x7fffde960000
probing at 0x80000001fffc

I assumed you wanted to reject those?

In either case, I recommend to tweak the VM layout, so that ld.so does 
not land closely to to the 128 TiB limit, so that the brk failure or 
returning of 48-bit addresses is avoided.

Thanks,
Florian