Re: [PATCH] net: tls: fix possible info leak in tls_set_device_offload()

[Hangyu Hua <hbh25y@gmail.com>]

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.