Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting

[David Hildenbrand]

On 07.10.21 05:01, Suren Baghdasaryan wrote:
> On Wed, Oct 6, 2021 at 7:53 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> > On Wed, 6 Oct 2021 19:46:57 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
> >
> > > > > > > I wish it was that simple and for some names like [anon:.bss] or
> > > > > > > [anon:dalvik-zygote space] reserving a unique id would work, however
> > > > > > > some names like [anon:dalvik-/system/framework/boot-core-icu4j.art]
> > > > > > > are generated dynamically at runtime and include package name.
> > > > > >
> > > > > > Valuable information
> > > > >
> > > > > Yeah, I should have described it clearer the first time around.
> > > >
> > > > If it gets this fancy then the 80 char limit is likely to become a
> > > > significant limitation and the choice should be explained & justified.
> > > >
> > > > Why not 97?  1034?  Why not just strndup_user() and be done with it?
> > >
> > > The original patch from 8 years ago used 256 as the limit but Rasmus
> > > argued that the string content should be human-readable, so 80 chars
> > > seems to be a reasonable limit (see:
> > > https://lore.kernel.org/all/d8619a98-2380-ca96-001e-60fe9c6204a6@xxxxxxxxxxxxxxxxxx),
> > > which makes sense to me. We should be able to handle the 80 char limit
> > > by trimming it before calling prctl().
> >
> > What's the downside to making it unlimited?
>
> If we ignore the human-readability argument, I guess the possibility
> of abuse and increased memory consumption? I'm guessing parsing such a
> string is also easier if there is a known limit?

64k * 80 bytes already makes me nervous enough :)


--
Thanks,

David / dhildenb