linux-kernel - Re: [PATCH 1/1] linux/container_of.h: Warn about loss of constness

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Message-ID: <Y1ZUIEYcjQZMdSfp@smile.fi.intel.com>
Date:   Mon, 24 Oct 2022 12:00:16 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Cc:     Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH 1/1] linux/container_of.h: Warn about loss of constness

+ Kees

On Mon, Oct 24, 2022 at 10:45:25AM +0200, Greg Kroah-Hartman wrote:
> On Mon, Oct 24, 2022 at 10:43:52AM +0200, Greg Kroah-Hartman wrote:
> > On Mon, Oct 24, 2022 at 11:26:10AM +0300, Sakari Ailus wrote:
> > > container_of() casts the original type to another which leads to the loss
> > > of the const qualifier if it is not specified in the caller-provided type.
> > > This easily leads to container_of() returning a non-const pointer to a
> > > const struct which the C compiler does not warn about.

...

> > >   * @type:	the type of the container struct this is embedded in.
> > >   * @member:	the name of the member within the struct.
> > >   *
> > > + * WARNING: as container_of() casts the given struct to another, also the
> 
> Wrong function name here.
> 
> > > + * possible const qualifier of @ptr is lost unless it is also specified in
> > > + * @type. This is not a problem if the containing object is not const. Use with
> > > + * care.
> > 
> > Same comments here.
> 
> Wait, no one uses this macro, so why not just remove it entirely?

Kees, do you know why and what for we have container_of_safe()?

-- 
With Best Regards,
Andy Shevchenko