linux-kernel - Re: [PATCH 4.19 01/20] nfc: st21nfca: Fix potential buffer overflows in EVT

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Date:   Thu, 2 Jun 2022 18:12:30 +0200
From:   Pavel Machek <pavel@....cz>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        theflamefire89@...il.com
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jordy Zomer <jordy@...ing.systems>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        "David S. Miller" <davem@...emloft.net>,
        Denis Efremov <denis.e.efremov@...cle.com>
Subject: Re: [PATCH 4.19 01/20] nfc: st21nfca: Fix potential buffer overflows
 in EVT_TRANSACTION

Hi!

> commit 4fbcc1a4cb20fe26ad0225679c536c80f1648221 upstream.
> 
> It appears that there are some buffer overflows in EVT_TRANSACTION.
> This happens because the length parameters that are passed to memcpy
> come directly from skb->data and are not guarded in any way.
> 
> Signed-off-by: Jordy Zomer <jordy@...ing.systems>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Denis Efremov <denis.e.efremov@...cle.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

It seems that this patch causes an memory leak, transaction does not
seem to be freed in the error paths.

(I also wonder if the skb should be freed in the error paths...?)

Reported-by: <theflamefire89@...il.com>

>  drivers/nfc/st21nfca/se.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> --- a/drivers/nfc/st21nfca/se.c
> +++ b/drivers/nfc/st21nfca/se.c
> @@ -332,6 +332,11 @@ int st21nfca_connectivity_event_received
>  			return -ENOMEM;
>  
>  		transaction->aid_len = skb->data[1];
> +
> +		/* Checking if the length of the AID is valid */
> +		if (transaction->aid_len > sizeof(transaction->aid))
> +			return -EINVAL;
> +
>  		memcpy(transaction->aid, &skb->data[2],
>  		       transaction->aid_len);
>  
> @@ -341,6 +346,11 @@ int st21nfca_connectivity_event_received
>  			return -EPROTO;
>  
>  		transaction->params_len = skb->data[transaction->aid_len + 3];
> +
> +		/* Total size is allocated (skb->len - 2) minus fixed array members */
> +		if (transaction->params_len > ((skb->len - 2) - sizeof(struct nfc_evt_transaction)))
> +			return -EINVAL;
> +
>  		memcpy(transaction->params, skb->data +
>  		       transaction->aid_len + 4, transaction->params_len);
>  
> 

-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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