linux-kernel - Re: algif_hash: splice of data

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Date:	Sat, 20 Dec 2014 07:37:55 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	leroy christophe <christophe.leroy@....fr>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-crypto <linux-crypto@...r.kernel.org>,
	'LKML' <linux-kernel@...r.kernel.org>
Subject: Re: algif_hash: splice of data > 2**16

Am Donnerstag, 18. Dezember 2014, 13:22:20 schrieb leroy christophe:

Hi Christophe,

> Le 18/12/2014 13:15, Stephan Mueller a écrit :
> > Hi Herbert,
> > 
> > While testing the vmsplice/splice interface of algif_hash I was made
> > aware of the problem that data blobs larger than 16 pages do not seem to
> > be hashed properly.
> > 
> > For testing, a file is mmap()ed and handed to vmsplice / splice. If the
> > file is smaller than 2**16, the interface returns the proper hash.
> > However, when the file is larger, only the first 2**16 bytes seem to be
> > used.
> > 
> > When adding printk's to hash_sendpage, I see that this function is
> > invoked exactly 16 times where the first 15 invocations have the
> > MSG_MORE flag set and the last invocation does not have MSG_MORE.
> 
> Hi Stephan,
> 
> I have already noticed the same issue and proposed a patch, but I never
> got any feedback and it has never been merged, allthought I pinged it a
> few times.
> 
> See https://lkml.org/lkml/2014/4/18/276

After testing, this patch does not work for me. The operation still stops 
after 16 pages.
> 
> Christophe


-- 
Ciao
Stephan
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