Re: [syzbot] [PATCH net v2] nfc: nci: Fix uninit-value in nci_rx_work

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Subject: [PATCH net v2] nfc: nci: Fix uninit-value in nci_rx_work
Author: ryasuoka@redhat.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 0d26c8ec9993..ab07b5f69664 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -1463,6 +1463,16 @@ int nci_core_ntf_packet(struct nci_dev *ndev, __u16 opcode,
 				 ndev->ops->n_core_ops);
 }
 
+static bool nci_valid_size(struct sk_buff *skb, unsigned int header_size)
+{
+	if (skb->len < header_size ||
+	    !nci_plen(skb->data) ||
+	    skb->len < header_size + nci_plen(skb->data)) {
+		return false;
+	}
+	return true;
+}
+
 /* ---- NCI TX Data worker thread ---- */
 
 static void nci_tx_work(struct work_struct *work)
@@ -1516,30 +1526,36 @@ static void nci_rx_work(struct work_struct *work)
 		nfc_send_to_raw_sock(ndev->nfc_dev, skb,
 				     RAW_PAYLOAD_NCI, NFC_DIRECTION_RX);
 
-		if (!nci_plen(skb->data)) {
-			kfree_skb(skb);
-			break;
-		}
+		if (!skb->len)
+			goto invalid_pkt_free;
 
 		/* Process frame */
 		switch (nci_mt(skb->data)) {
 		case NCI_MT_RSP_PKT:
+			if (!nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
+				goto invalid_pkt_free;
 			nci_rsp_packet(ndev, skb);
 			break;
 
 		case NCI_MT_NTF_PKT:
+			if (!nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
+				goto invalid_pkt_free;
 			nci_ntf_packet(ndev, skb);
 			break;
 
 		case NCI_MT_DATA_PKT:
+			if (!nci_valid_size(skb, NCI_DATA_HDR_SIZE))
+				goto invalid_pkt_free;
 			nci_rx_data_packet(ndev, skb);
 			break;
 
 		default:
 			pr_err("unknown MT 0x%x\n", nci_mt(skb->data));
-			kfree_skb(skb);
-			break;
+			goto invalid_pkt_free;
 		}
+invalid_pkt_free:
+		kfree_skb(skb);
+		break;
 	}
 
 	/* check if a data exchange timeout has occurred */