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Date: Fri, 23 Feb 2018 13:17:15 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: SF Markus Elfring <elfring@users.sourceforge.net>
Cc: target-devel@vger.kernel.org, David Disseldorp <ddiss@suse.de>,
        kernel-janitors@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        linux-scsi@vger.kernel.org
Subject: Re: [0/8] target-iSCSI: Adjustments for several function
 implementations
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On Fri, Feb 23, 2018 at 10:06:16AM +0100, SF Markus Elfring wrote:
> > Calling crypto_free_shash(NULL) is actually fine.
> 
> Really?
> 
> 
> > It doesn't dereference the parameter, it just does pointer math on it in
> > crypto_shash_tfm() and returns if it's NULL in crypto_destroy_tfm().
> 
> Can a passed null pointer really work in this function?
> 
> https://elixir.bootlin.com/linux/v4.16-rc2/source/include/crypto/hash.h#L684
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/crypto/hash.h?id=0f9da844d87796ac31b04e81ee95e155e9043132#n751
> 
> static inline struct crypto_tfm *crypto_shash_tfm(struct crypto_shash *tfm)
> {
> 	return &tfm->base;
> }

Yes.  It's not a dereference, it's just doing pointer math to get the
address.

regards,
dan carpenter