Re: [PATCH 0/7] hwmon: zero-initialization instead of memset

[Manish Baing]

Hi Guenter,

Thank you for catching the struct padding risk. You are completely
right—Patch 7 (it87.c) would trigger a KMSAN uninit-value warning due
to the kmemdup() copy in platform_device_add_data(). I will drop that
patch entirely.

I have audited the other six drivers in this series and verified that
their variables are never passed to memcmp(), kmemdup(), or hashed, so
the = {} initialization is perfectly safe there.

While this does not fix an active bug, the goal is to follow a cleanup
pattern  recently discussed for the IIO subsystem [1],[2]
1.Better performance: It removes the need for an extra function call.
Instead, the compiler clears the memory directly and more efficiently.
2.Safer code: It prevents accidental memory leaks that happen when
developers make a typo in the sizeof() calculation.

Would you be open to a v2 that includes just the six safe patches to
modernize these initializations?

[1] https://lore.kernel.org/all/20250611-iio-zero-init-stack-with-instead-of-memset-v1-0-ebb2d0a24302@xxxxxxxxxxxx/
[2] https://lore.kernel.org/linux-iio/202505090942.48EBF01B@keescook/

Thanks for your time and guidance,

Thanks & Regards,
Manish

On Sun, Jun 7, 2026 at 9:42 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 5/30/26 15:13, Manish Baing wrote:
> > Hi all,
> >
> > This patch series cleans up memory initialization across several
> > hardware monitoring (hwmon) drivers by replacing explicit memset() calls
> > with empty brace initialization (= {}).
> >
> > Following similar cleanups in the IIO subsystem [1], this series updates
> > these drivers to stop using memset() for stack memory initialization.
> > As noted in those discussions [2], using empty brace initialization (= {})
> > is the preferred approach.
> >
> > Beyond simple replacements, a few drivers (nct6683, nct6775-platform, it87)
> > were using memset() inside a for-loop. To fix this, the variable
> > declarationwas moved directly inside the loop and zero-initialized there.
> > This safely resets the data on every iteration and makes the code much
> > cleaner.
> >
> > Testing:
> > - Compiled all modified files using `make W=1` with no warnings or errors.
> >
> > [1]: https://lore.kernel.org/all/20250611-iio-zero-init-stack-with-instead-of-memset-v1-0-ebb2d0a24302@xxxxxxxxxxxx/
> > [2]: https://lore.kernel.org/linux-iio/202505090942.48EBF01B@keescook/
>
> That discussion does not fully address a problem I had seen previously,
> where {} did _not_ zero-fill all holes, causing subsequent memcmp()
> failures on affected data structures. It took a lot a lot of debugging
> to find and fix that problem. Given that, I am not inclined to accept
> this series unless someone convinces me that it fixes an actual problem
> _and_ that each and every instance of the changes is not used in a
> subsequent memcmp().
>
> Guenter
>