linux-kernel - Re: [PATCH] net: tls: fix possible info leak in tls_set_device

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Message-ID: <04c4d6ee-f893-5248-26cf-2c6d1c9b3aa5@gmail.com>
Date:   Fri, 24 Feb 2023 11:33:29 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     Sabrina Dubroca <sd@...asysnail.net>
Cc:     borisp@...dia.com, john.fastabend@...il.com, kuba@...nel.org,
        davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: tls: fix possible info leak in
 tls_set_device_offload()

On 24/2/2023 11:07, Hangyu Hua wrote:
> On 23/2/2023 19:15, Sabrina Dubroca wrote:
>> 2023-02-23, 17:05:08 +0800, Hangyu Hua wrote:
>>> After tls_set_device_offload() fails, we enter tls_set_sw_offload(). But
>>> tls_set_sw_offload can't set cctx->iv and cctx->rec_seq to NULL if it 
>>> fails
>>> before kmalloc cctx->iv. This may cause info leak when we call
>>> do_tls_getsockopt_conf().
>>
>> Is there really an issue here?
>>
>> If both tls_set_device_offload and tls_set_sw_offload fail,
>> do_tls_setsockopt_conf will clear crypto_{send,recv} from the context.
>> Then the TLS_CRYPTO_INFO_READY in do_tls_getsockopt_conf will fail, so
>> we won't try to access iv or rec_seq.
>>
> 
> My bad. I forget memzero_explicit. Then this is harmless. But I still 
> think it is better to set them to NULL like tls_set_sw_offload's error 
> path because we don't know there are another way to do this(I will 
> change the commit log). What do you think?

Like a rare case, there is a race condition between
do_tls_getsockopt_conf and do_tls_setsockopt_conf while the previous
condition is met. TLS_CRYPTO_INFO_READY(crypto_info) is not
protected by lock_sock in do_tls_getsockopt_conf. It's just too
difficult to satisfy both conditions at the same time.