From: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
To: Jordy Zomer <jordy@pwning.systems>, linux-kernel@vger.kernel.org
Cc: wengjianfeng <wengjianfeng@yulong.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org
Subject: Re: [PATCH v2] nfc: st-nci: Fix potential buffer overflows in EVT_TRANSACTION
Date: Thu, 18 Nov 2021 08:36:26 +0100 [thread overview]
Message-ID: <f5bdd108-155d-0426-77e6-841994953719@canonical.com> (raw)
In-Reply-To: <20211118070202.2739158-1-jordy@pwning.systems>
On 18/11/2021 08:02, Jordy Zomer wrote:
> 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.
>
> It would be nice if someone can review and test this patch because
> I don't own the hardware :)
Thanks for your patch.
You mentioned that there are buffer overflows but you do not own the
hardware. How do you know these overflow exist? How did you detect them?
>
> EDIT: Changed comment style and double newlines
Please add changelog after --- separators so it does not clutter the
commit log with unrelated "EDIT".
>
> Signed-off-by: Jordy Zomer <jordy@pwning.systems>
> ---
> drivers/nfc/st-nci/se.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c
> index 7764b1a4c3cf..8e2ac8a3d199 100644
> --- a/drivers/nfc/st-nci/se.c
> +++ b/drivers/nfc/st-nci/se.c
> @@ -335,6 +335,11 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev,
> 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;
I am thinking whether the check should be before memory allocation - to
save on useless memory allocation in case of error, but make the code
less obvious with referring to skb->data[1] twice.
> +
> memcpy(transaction->aid, &skb->data[2], transaction->aid_len);
>
> /* Check next byte is PARAMETERS tag (82) */
> @@ -343,6 +348,16 @@ static int st_nci_hci_connectivity_event_received(struct nci_dev *ndev,
> return -EPROTO;
>
> transaction->params_len = skb->data[transaction->aid_len + 3];
> +
> + /*
> + * check if the length of the parameters is valid
> + * we can't use sizeof(transaction->params) because it's
> + * a flexible array member so we have to check if params_len
> + * is bigger than the space allocated for the array
> + */
> + if (transaction->params_len > ((skb->len - 2) - sizeof(struct nfc_evt_transaction)))
> + return -EINVAL;
The current comment is long and actually not explaining how you get "-2"
and sizeof, so how about:
"Total size is allocated (skb->len - 2) minus fixed array members)"
In general the code looks ok, although I cannot provide tests.
> +
> memcpy(transaction->params, skb->data +
> transaction->aid_len + 4, transaction->params_len);
>
>
Best regards,
Krzysztof
next prev parent reply other threads:[~2021-11-18 7:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-17 17:15 [PATCH] nfc: st-nci: Fix potential buffer overflows in EVT_TRANSACTION Jordy Zomer
2021-11-18 4:42 ` Jakub Kicinski
2021-11-18 7:02 ` [PATCH v2] " Jordy Zomer
2021-11-18 7:36 ` Krzysztof Kozlowski [this message]
2022-01-11 16:45 ` [PATCH v3] " Jordy Zomer
2022-01-12 10:07 ` Krzysztof Kozlowski
2022-01-12 17:34 ` Jakub Kicinski
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