linux-kernel - Re: [PATCH v1 1/5] memremap: Check for size parameter

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Message-ID: <20200415145855.GM185537@smile.fi.intel.com>
Date:   Wed, 15 Apr 2020 17:58:55 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Christoph Hellwig <hch@....de>
Cc:     linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>,
        Arnd Bergmann <arnd@...db.de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>
Subject: Re: [PATCH v1 1/5] memremap: Check for size parameter

On Sat, Nov 16, 2019 at 05:29:37PM +0100, Christoph Hellwig wrote:
> On Fri, Nov 15, 2019 at 08:00:40PM +0200, Andy Shevchenko wrote:
> > There is no use of memremap() to be called with size = 0.
> > Simple return NULL pointer and allow callers to drop this check.
> 
> Given that this really is an error condition, maybe a WARN_ON_ONCE
> would fit here?

It appears some users are using defensive programming and rely simple on error
code. I dunno if they are really expect to have size == 0 in some (non-fatal)
cases.

-- 
With Best Regards,
Andy Shevchenko