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SubjectRe: [PATCH 1/1] NFC: Fix possible memory corruption when handling SHDLC I-Frame commands
On Wed, Aug 15, 2018 at 09:40:13AM -0700, Suren Baghdasaryan wrote:
> On Wed, Aug 15, 2018 at 1:29 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > On Tue, Aug 14, 2018 at 03:38:14PM -0700, Suren Baghdasaryan wrote:
> >> The separate fix for the size of pipes[] array is posted here:
> >> https://lkml.org/lkml/2018/8/14/1034
> >> Thanks!
> >>
> >
> > That's great! Let's add some bounds checking to nfc_hci_msg_rx_work()
> > and nfc_hci_recv_from_llc() as well and then we can close the chapter on
> > these bugs.
>
> Dan, I don't think we need additional checks there. Here are the
> relevant parts of the code in nfc_hci_recv_from_llc():
>

Sorry, I meant after that at the end of the function:

net/nfc/hci/core.c
902 /* if this is a response, dispatch immediately to
903 * unblock waiting cmd context. Otherwise, enqueue to dispatch
904 * in separate context where handler can also execute command.
905 */
906 packet = (struct hcp_packet *)hcp_skb->data;
907 type = HCP_MSG_GET_TYPE(packet->message.header);
908 if (type == NFC_HCI_HCP_RESPONSE) {
909 pipe = packet->header;
^^^^^^^^^^^^^^^^^^^^^
Pipe can go up to 255.

910 instruction = HCP_MSG_GET_CMD(packet->message.header);
911 skb_pull(hcp_skb, NFC_HCI_HCP_PACKET_HEADER_LEN +
912 NFC_HCI_HCP_MESSAGE_HEADER_LEN);
913 nfc_hci_hcp_message_rx(hdev, pipe, type, instruction, hcp_skb);
^^^^
Then inside the nfc_hci_hcp_message_rx() function we call
nfc_hci_cmd_received() and nfc_hci_event_received() which use it as an
array index.

914 } else {
915 skb_queue_tail(&hdev->msg_rx_queue, hcp_skb);
916 schedule_work(&hdev->msg_rx_work);
917 }
918 }

It's the same thing when nfc_hci_hcp_message_rx() is called from
nfc_hci_msg_rx_work():

138 static void nfc_hci_msg_rx_work(struct work_struct *work)
139 {
140 struct nfc_hci_dev *hdev = container_of(work, struct nfc_hci_dev,
141 msg_rx_work);
142 struct sk_buff *skb;
143 struct hcp_message *message;
144 u8 pipe;
145 u8 type;
146 u8 instruction;
147
148 while ((skb = skb_dequeue(&hdev->msg_rx_queue)) != NULL) {
149 pipe = skb->data[0];
^^^^^^^^^^^^^^^^^^^
150 skb_pull(skb, NFC_HCI_HCP_PACKET_HEADER_LEN);
151 message = (struct hcp_message *)skb->data;
152 type = HCP_MSG_GET_TYPE(message->header);
153 instruction = HCP_MSG_GET_CMD(message->header);
154 skb_pull(skb, NFC_HCI_HCP_MESSAGE_HEADER_LEN);
155
156 nfc_hci_hcp_message_rx(hdev, pipe, type, instruction, skb);
^^^^
157 }
158 }

regards,
dan carpenter

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