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Date:   Fri, 24 Aug 2018 09:00:00 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@redhat.com>
To:     Herbert Xu <herbert@gondor.apana.org.au>
cc:     "David S. Miller" <davem@davemloft.net>,
        linux-crypto@vger.kernel.org, Mike Snitzer <msnitzer@redhat.com>,
        dm-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: Deadlock when using crypto API for block devices
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On Fri, 24 Aug 2018, Mikulas Patocka wrote:

> 
> 
> On Fri, 24 Aug 2018, Herbert Xu wrote:
> 
> > On Fri, Aug 24, 2018 at 07:06:32AM -0400, Mikulas Patocka wrote:
> > >
> > > A quick search through the crypto code shows that ahash_save_req and 
> > > seqiv_aead_encrypt return -ENOMEM.
> > > 
> > > Will you fix them?
> > 
> > These only trigger for unaligned buffers.  It would be much better
> > if dm-crypt can ensure that the input/output is properly unaligned
> > and if otherwise do the allocation in dm-crypt.
> 
> But we are relying here on an implementation detail and not on contract.
> 
> Mikulas

BTW. gcmaes_crypt_by_sg also contains GFP_ATOMIC and -ENOMEM, behind a 
pretty complex condition. Do you mean that this condition is part of the 
contract that the crypto API provides?

Should "req->src->offset + req->src->length < PAGE_SIZE" use "<=" instead? 
Because if the data ends up at page boundary, it will use the atomic 
allocation that can fail.

Mikulas