linux-kernel - Re: [PATCH v4] gpio: sim: fix an invalid _

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Message-ID: <ZQl8tkWnQcjtFBbQ@smile.fi.intel.com>
Date:   Tue, 19 Sep 2023 13:49:26 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     brgl@...ev.pl
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        akpm@...ux-foundation.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4] gpio: sim: fix an invalid __free() usage

On Tue, Sep 19, 2023 at 12:31:36AM -0700, brgl@...ev.pl wrote:
> On Mon, 18 Sep 2023 17:31:36 +0200, Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> said:
> > On Mon, Sep 18, 2023 at 04:55:33PM +0200, Bartosz Golaszewski wrote:

...

> > Of course this can be replace with...
> >
> >> +		line_names = kcalloc(line_names_size, sizeof(*line_names),
> >> +				     GFP_KERNEL);
> >
> >> +		if (!line_names)
> >
> > ZERO_OR_NULL_PTR() check here, but I assume we discourage use of it.
> 
> Why? There are less than 40 instances of using it in the kernel. kmalloc()
> returns NULL on failure.

Nope, k*alloc*() returns ZERO or NULL on failure. That's what most developers
are missing :-)

> >> +			return ERR_PTR(-ENOMEM);

Hence either one needs to check for 0 the size given to the kmalloc(),
_or_ to check for all possible return values from it.

-- 
With Best Regards,
Andy Shevchenko