linux-kernel - Re: Deadlock when using crypto API for block devices

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Message-ID: <20180824132145.2zsnqwbih3iygeeq@gondor.apana.org.au>
Date:   Fri, 24 Aug 2018 21:21:45 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, Mike Snitzer <msnitzer@...hat.com>,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: Deadlock when using crypto API for block devices

On Fri, Aug 24, 2018 at 09:00:00AM -0400, Mikulas Patocka wrote:
>
> 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?

This is an implementation defect.  I think for this case we should
fall back to software GCM if the accelerated version fails.

> 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.

This condition does look strange.  It's introduced by the commit
e845520707f85c539ce04bb73c6070e9441480be.   Dave, what exactly is
it meant to do?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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