linux-kernel - Re: [PATCH v5 2/4] crypto: ti - Add support for AES-CTR in DTHEv2 driver

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Message-ID: <aQxM2z9kC6sTqBZ5@gondor.apana.org.au>
Date: Thu, 6 Nov 2025 15:23:07 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: T Pratham <t-pratham@...com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Manorit Chawdhry <m-chawdhry@...com>,
	Kamlesh Gurudasani <kamlesh@...com>,
	Shiva Tripathi <s-tripathi1@...com>,
	Kavitha Malarvizhi <k-malarvizhi@...com>,
	Vishal Mahaveer <vishalm@...com>,
	Praneeth Bajjuri <praneeth@...com>, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/4] crypto: ti - Add support for AES-CTR in DTHEv2
 driver

On Fri, Oct 31, 2025 at 08:11:34PM +0530, T Pratham wrote:
>
> Let me know if this is fine.

Yes I think this should work.

> However, I suppose we similarly cannot do allocations in AEADs as well?
> If that is the case, my current code relies a lot on it (using sg_split
> to separate AAD from {plain, cipher}text and applying padding like CTR
> here, both of which allocate memory).
> 
> I can change padding to avoid kmallocs like CTR easily. But separating
> AAD and plaintext/ciphertext without using sg_split will be a task. Let
> me know if this is correct, so that I'll split the series and send
> ciphers now, and AEADs later.

OK it's not totally forbidden to allocate memory.  However, you
should only use GFP_ATOMIC to avoid dead-lock (GFP_KERNEL can
trigger writes to storage, which can in turn call crypto), and
provide a fallback path to software crypto when the allocation
fails.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt