linux-kernel - Re: [PATCH] pstore: Tidy up an error check

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Message-ID: <20201202200021.GJ2789@kadam>
Date:   Wed, 2 Dec 2020 23:00:21 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] pstore: Tidy up an error check

On Wed, Dec 02, 2020 at 11:25:46AM -0800, Kees Cook wrote:
> On Wed, Dec 02, 2020 at 09:45:31AM +0300, Dan Carpenter wrote:
> > The crypto_alloc_comp() function never returns NULL, it returns error
> > pointers on error.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> I replied to an identical patch yesterday, actually:
> https://lore.kernel.org/lkml/202012011215.B9BF24A6D@keescook/ 
> 
> Using IS_ERR_OR_NULL() is more robust, and this isn't fast path, so I'd
> prefer to keep it that way.
> 

The NULL return doesn't make any sense though because crypto_alloc_comp()
isn't optional...  When a function returns both error pointers and NULLs
then the NULL is special kind of success.

	p = get_feature();

If "p" is an error pointer that means an error happened.  If "p" is NULL
that means the feature is disabled in the .config or whatever.  We can't
return a valid pointer because the feature doesn't exist but it's also
not an error so it doesn't return an error pointer.  The code should
not print a warning, maybe an info level printk at most.  Then the
driver should continue operating with the feature turned off.

Two of the callers for crypto_alloc_comp() check for error pointers and
NULL and three only check for error pointers.  It's inconsistent.

regards,
dan carpenter