Re: [RFC v3 5/7] mm: Fix benign off-by-one bugs

[Alejandro Colomar <alx@kernel.org>]

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Hi Michal,

On Mon, Jul 07, 2025 at 09:53:31AM +0200, Michal Hocko wrote:
> On Mon 07-07-25 09:46:12, Marco Elver wrote:
> > On Mon, 7 Jul 2025 at 07:06, Alejandro Colomar <alx@kernel.org> wrote:
> > >
> > > We were wasting a byte due to an off-by-one bug.  s[c]nprintf()
> > > doesn't write more than $2 bytes including the null byte, so trying to
> > > pass 'size-1' there is wasting one byte.  Now that we use seprintf(),
> > > the situation isn't different: seprintf() will stop writing *before*
> > > 'end' --that is, at most the terminating null byte will be written at
> > > 'end-1'--.
> > >
> > > Fixes: bc8fbc5f305a (2021-02-26; "kfence: add test suite")
> > > Fixes: 8ed691b02ade (2022-10-03; "kmsan: add tests for KMSAN")
> > 
> > Not sure about the Fixes - this means it's likely going to be
> > backported to stable kernels, which is not appropriate. There's no
> > functional problem, and these are tests only, so not worth the churn.
> 
> As long as there is no actual bug fixed then I believe those Fixes tags
> are more confusing than actually helpful. And that applies to other
> patches in this series as well.

For the dead code, I can remove the fixes tags, and even the changes
themselves, since there are good reasons to keep the dead code
(consistency, and avoiding a future programmer forgetting to add it back
when adding a subsequent seprintf() call).

For the fixes to UB, do you prefer the Fixes tags to be removed too?


Have a lovely day!
Alex

> -- 
> Michal Hocko
> SUSE Labs

-- 
<https://www.alejandro-colomar.es/>

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