linux-kernel - Re: [PATCH 00/28] iio: zero init stack with { } instead of memset()

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Message-ID: <20250614131844.7fdc10b8@jic23-huawei>
Date: Sat, 14 Jun 2025 13:18:44 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Pavel Machek <pavel@....cz>
Cc: Andy Shevchenko <andriy.shevchenko@...el.com>, Nicolas Frattaroli
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Subject: Re: [PATCH 00/28] iio: zero init stack with { } instead of memset()

On Sat, 14 Jun 2025 08:47:25 +0200
Pavel Machek <pavel@....cz> wrote:

> On Thu 2025-06-12 22:10:07, Andy Shevchenko wrote:
> > On Thu, Jun 12, 2025 at 08:54:07PM +0200, Pavel Machek wrote:  
> > > > On Thursday, 12 June 2025 11:17:52 Central European Summer Time Pavel Machek wrote:  
> > > > >   
> > > > > > Jonathan mentioned recently that he would like to get away from using
> > > > > > memset() to zero-initialize stack memory in the IIO subsystem. And we
> > > > > > have it on good authority that initializing a struct or array with = { }
> > > > > > is the preferred way to do this in the kernel [1]. So here is a series
> > > > > > to take care of that.  
> > > > > 
> > > > > 1) Is it worth the churn?
> > > > > 
> > > > > 2) Will this fail to initialize padding with some obscure compiler?  
> > > > 
> > > > as of right now, the only two C compilers that are supported are
> > > > GCC >= 8.1, and Clang >= 13.0.1. If anyone even manages to get the
> > > > kernel  
> > > 
> > > Well... I'm pretty sure parts of this would make it into -stable as a
> > > dependency, or because AUTOSEL decides it is a bugfix. So..
> > > 
> > > GNU C                  4.9              gcc --version
> > > Clang/LLVM (optional)  10.0.1           clang --version  
> > 
> > Even though, what the kernel versions are you referring to? I am sure there
> > plenty of cases with {} there.  
> 
> 5.10, for example. I'm sure they are, uninitialized padding is a
> security hole, but rather hard to detect if they are not specifically
> looking.

The stack kunit test is there back to 5.0-rc4 
50ceaa95ea09 ("lib: Introduce test_stackinit module")

So I think we should be pretty well defended against issues.

Hence I plan to pick this up curently.

Thanks all for inputs on this.

Fun corners of the C spec vs implementations!

Jonathan

> 
> BR,
> 								Pavel