linux-kernel - Re: [PATCH 0/2] maple_tree: Fix mas

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Message-ID: <20230921185330.j5jw3oms4tc6crkf@revolver>
Date:   Thu, 21 Sep 2023 14:53:30 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     maple-tree@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pedro.falcato@...il.com,
        stable <stable@...nel.org>
Subject: Re: [PATCH 0/2] maple_tree: Fix mas_prev() state regression.

* Andrew Morton <akpm@...ux-foundation.org> [230921 14:25]:
> On Thu, 21 Sep 2023 14:12:34 -0400 "Liam R. Howlett" <Liam.Howlett@...cle.com> 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@...r.kernel.org, although stable@...nel.org works just fine.