Re: [PATCH 0/2] maple_tree: Fix mas_prev() state regression.

[Liam R. Howlett]

* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> [230921 14:25]:
> On Thu, 21 Sep 2023 14:12:34 -0400 "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> wrote:
> 
> > Pedro Falcato contacted me on IRC with an mprotect regression which was
> > bisected back to the iterator changes for maple tree.  Root cause
> > analysis showed the mas_prev() running off the end of the VMA space
> > (previous from 0) followed by mas_find(), would skip the first value.
> > 
> > This patch set introduces maple state underflow/overflow so the sequence
> > of calls on the maple state will return what the user expects.
> 
> It isn't clear what are the user-visible effects of this flaw?  Please
> send this along and I'll paste it in.


User may notice that mas_prev() or mas_next() calls that result in going
outside of the limit passed to the call will cause incorrect returns on
subsequent calls using that maple state, such as mas_find() skipping an
entry.

> 
> Patch 1 should be titled "Add mas_is_active ...".

Oh yes, sorry.

> 
> And patch 1 should have had cc:stable in the changelog.

Ah, I sent the series to stable but didn't add that to the changelog.
I'll do that in v2 as it seems I need to update patch 2 anyways.

> 
> It's stable@xxxxxxxxxxxxxxx, although stable@xxxxxxxxxx works just fine.