linux-kernel - Re: algif_hash: splice of data

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Message-ID: <20272672.S6U6VsnYQl@tauon>
Date:	Thu, 18 Dec 2014 13:37:48 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	leroy christophe <christophe.leroy@....fr>,
	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	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 Leroy, Herbert,

>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

Thanks a lot for pointing to this patch.

Herbert, do you see a problem in this patch? If no, would it be possible 
that you ping the VFS maintainer as I guess your word carries more 
weight?

In any case, I will test that patch tonight.

Thanks
Stephan
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