netdev - Re: [PATCH V2 net 1/1] net/tls(TLS_SW): Fix list_del double free caused by a race condition in tls_tx

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Date:   Wed, 18 Sep 2019 14:45:28 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Pooja Trivedi <poojatrivedi@...il.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, daniel@...earbox.net,
        john.fastabend@...il.com, davejwatson@...com, aviadye@...lanox.com,
        borisp@...lanox.com, Pooja Trivedi <pooja.trivedi@...ckpath.com>,
        Mallesham Jatharakonda <mallesh537@...il.com>
Subject: Re: [PATCH V2 net 1/1] net/tls(TLS_SW): Fix list_del double free
 caused by a race condition in tls_tx_records

On Wed, 18 Sep 2019 17:37:44 -0400, Pooja Trivedi wrote:
> Hi Jakub,
> 
> I have explained one potential way for the race to happen in my
> original message to the netdev mailing list here:
> https://marc.info/?l=linux-netdev&m=156805120229554&w=2
> 
> Here is the part out of there that's relevant to your question:
> 
> -----------------------------------------
> 
> One potential way for race condition to appear:
> 
> When under tcp memory pressure, Thread 1 takes the following code path:
> do_sendfile ---> ... ---> .... ---> tls_sw_sendpage --->
> tls_sw_do_sendpage ---> tls_tx_records ---> tls_push_sg --->
> do_tcp_sendpages ---> sk_stream_wait_memory ---> sk_wait_event

Ugh, so do_tcp_sendpages() can also release the lock :/

Since the problem occurs in tls_sw_do_sendpage() and
tls_sw_do_sendmsg() as well, should we perhaps fix it at that level?