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

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Message-ID: <CAKbZUD3GS7YJmeO1q=f7LRomkJAigQaFw93Vwn99jZaO9O1Eyg@mail.gmail.com>
Date:   Fri, 22 Sep 2023 00:41:37 +0100
From:   Pedro Falcato <pedro.falcato@...il.com>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        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.

On Fri, Sep 22, 2023 at 12:34 AM Liam R. Howlett
<Liam.Howlett@...cle.com> wrote:
>
> * Andrew Morton <akpm@...ux-foundation.org> [230921 19:27]:
> > On Thu, 21 Sep 2023 20:23:11 +0100 Matthew Wilcox <willy@...radead.org> wrote:
> >
> > > > > 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.
> > >
> > > When Andrew says "User visible" he means "userspace visible".  Not
> > > "in kernel user visible".  What are the _consequences_.
> >
> > Thanks ;)
> >
> > We have a Link:
> > (https://gist.github.com/heatd/85d2971fae1501b55b6ea401fbbe485b) but it
> > takes us to the reproducer code.  If it took us to Pedro's initial bug
> > report then the sun would shine and birds would sing.
> >
>
> I don't think the irc channel is logged so I'll respin with a cleaner
> changelog for both patches and the subject of patch 1.

FYI:

The original distro bug report: https://bugs.archlinux.org/task/79656
The original userspace program bug report:
https://github.com/cebix/macemu/issues/271

(and yes, this is my fault, I should've raised this on the ML with the
regression tracker and all, but I tried to write my own fix then
realized it was trickier than it looked and pinged Liam)

-- 
Pedro