nfc: nci: free rx_data_reassembly skb on NCI device cleanup

rx_data_reassembly skb is stored during NCI data exchange for processing
fragmented packets. It is dropped only when the last fragment is processed
or when an NTF packet with NCI_OP_RF_DEACTIVATE_NTF opcode is received.
However, the NCI device may be deallocated before that which leads to skb
leak.

As by design the rx_data_reassembly skb is bound to the NCI device and
nothing prevents the device to be freed before the skb is processed in
some way and cleaned, free it on the NCI device cleanup.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 6a2968aa ("NFC: basic NCI protocol implementation")
Cc: stable@vger.kernel.org
Reported-by: syzbot+6b7c68d9c21e4ee4251b@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000f43987060043da7b@google.com/Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/nfc/nci/core.c

@@ -1208,6 +1208,10 @@ void nci_free_device(struct nci_dev *ndev)
 {
 	nfc_free_device(ndev->nfc_dev);
 	nci_hci_deallocate(ndev);
+
+	/* drop partial rx data packet if present */
+	if (ndev->rx_data_reassembly)
+		kfree_skb(ndev->rx_data_reassembly);
 	kfree(ndev);
 }
 EXPORT_SYMBOL(nci_free_device);