netdev - Re: [PATCH] net: tls: fix a memory leak bug

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Date:   Wed, 24 Apr 2019 18:08:40 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Wenwen Wang <wang6495@....edu>
Cc:     Boris Pismenny <borisp@...lanox.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        Dave Watson <davejwatson@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        netdev@...r.kernel.org (open list:NETWORKING [TLS]),
        linux-kernel@...r.kernel.org (open list),
        Vakul Garg <vakul.garg@....com>
Subject: Re: [PATCH] net: tls: fix a memory leak bug

On Wed, 24 Apr 2019 15:18:07 -0500, Wenwen Wang wrote:
> In decrypt_internal(), a memory block 'mem' is allocated through kmalloc()
> to hold aead_req, sgin[], sgout[], aad, and iv. This memory block should be
> freed after it is used, before this function is returned. However, if the
> return value of the function invocation of tls_do_decryption() is
> -EINPROGRESS, this memory block is actually not freed, which is a memory
> leak bug.
> 
> To fix this issue, free the allocated block before the error code
> -EINPROGRESS is returned.
> 
> Signed-off-by: Wenwen Wang <wang6495@....edu>

Did you find this by code inspection or is this provable at runtime
(kmemleak or such)?

> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index b50ced8..22445bb 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -1445,8 +1445,10 @@ static int decrypt_internal(struct sock *sk, struct sk_buff *skb,
>  	/* Prepare and submit AEAD request */
>  	err = tls_do_decryption(sk, skb, sgin, sgout, iv,
>  				data_len, aead_req, async);
> -	if (err == -EINPROGRESS)
> +	if (err == -EINPROGRESS) {
> +		kfree(mem);
>  		return err;

Mm... don't think so.

-EINPROGRESS is special, it means something is working on the request
asynchronously here.

I think this memory is freed in tls_decrypt_done():

	kfree(aead_req);

Note that aead_req is the first member of the allocated buffer.

CCing Vakul

> +	}
>  
>  	/* Release the pages in case iov was mapped to pages */
>  	for (; pages > 0; pages--)