netdev - Re: [PATCH net-next] tls: Fix socket mem accounting error under async encryption

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Date:   Tue, 25 Sep 2018 10:44:16 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     vakul.garg@....com
Cc:     netdev@...r.kernel.org, borisp@...lanox.com, aviadye@...lanox.com,
        davejwatson@...com, doronrk@...com
Subject: Re: [PATCH net-next] tls: Fix socket mem accounting error under
 async encryption

From: Vakul Garg <vakul.garg@....com>
Date: Tue, 25 Sep 2018 16:26:17 +0530

> Current async encryption implementation sometimes showed up socket
> memory accounting error during socket close. This results in kernel
> warning calltrace. The root cause of the problem is that socket var
> sk_forward_alloc gets corrupted due to access in sk_mem_charge()
> and sk_mem_uncharge() being invoked from multiple concurrent contexts
> in multicore processor. The apis sk_mem_charge() and sk_mem_uncharge()
> are called from functions alloc_plaintext_sg(), free_sg() etc. It is
> required that memory accounting apis are called under a socket lock.
> 
> The plaintext sg data sent for encryption is freed using free_sg() in
> tls_encryption_done(). It is wrong to call free_sg() from this function.
> This is because this function may run in irq context. We cannot acquire
> socket lock in this function.
> 
> We remove calling of function free_sg() for plaintext data from
> tls_encryption_done() and defer freeing up of plaintext data to the time
> when the record is picked up from tx_list and transmitted/freed. When
> tls_tx_records() gets called, socket is already locked and thus there is
> no concurrent access problem.
> 
> Fixes: a42055e8d2c3 ("net/tls: Add support for async encryption")
> Signed-off-by: Vakul Garg <vakul.garg@....com>

Applied.