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

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Date:   Fri, 24 Feb 2023 17:35:01 +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 15:57, Sabrina Dubroca wrote:
> 2023-02-24, 11:33:29 +0800, Hangyu Hua wrote:
>> 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?
> 
> Yes, I guess for consistency between functions it would be ok.
> 
>> 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.
> 
> Ugh, thanks for noticing this. We should move the lock_sock in
> getsockopt before TLS_CRYPTO_INFO_READY. Do you want to write that
> patch?
> 
> Thanks.
> 

I see. I will make a new patch to fix the race and send v2 of this.

Thanks,
Hangyu