linux-kernel - Re: [PATCH next] crypto: fix oob Read in arc4

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Message-ID: <ZYOEedosh0ObHgMq@gondor.apana.org.au>
Date: Thu, 21 Dec 2023 08:19:05 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Edward Adam Davis <eadavis@...com>
Cc: syzbot+8ffb0839a24e9c6bfa76@...kaller.appspotmail.com,
	davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH next] crypto: fix oob Read in arc4_crypt

On Wed, Dec 20, 2023 at 11:53:55PM +0800, Edward Adam Davis wrote:
> The space allocated to areq is not sufficient to access the member __ctx of 
> struct skcipher_request, as the space occupied by struct arc4_ctx for reading 
> is 1032 bytes, while the requested memory size in skcipher_recvmsg() is:
> sizeof(struct af_alg_async_req) + crypto_skcipher_reqsize(tfm) = 736 bytes,
> which does not include the memory required for __ctx of struct skcipher_request.

I cannot reproduce this.  The total allocated size I get is 1768.

How can crypto_skcipher_reqsize(tfm) return zero?

Thanks,
-- 
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