Re: [syzbot] [PATCH net v5] nfc: nci: Fix uninit-value in nci_rx_work

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Subject: [PATCH net v5] nfc: nci: Fix uninit-value in nci_rx_work
Author: ryasuoka@xxxxxxxxxx

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

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index b133dc55304c..7a9897fbf4f4 100644
--- a/net/nfc/nci/core.c
+++ b/net/nfc/nci/core.c
@@ -1463,6 +1463,19 @@ 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)
+{
+	BUILD_BUG_ON(NCI_CTRL_HDR_SIZE != NCI_DATA_HDR_SIZE);
+	unsigned int hdr_size = NCI_CTRL_HDR_SIZE;
+
+	if (skb->len < hdr_size ||
+	    !nci_plen(skb->data) ||
+	    skb->len < hdr_size + nci_plen(skb->data)) {
+		return false;
+	}
+	return true;
+}
+
 /* ---- NCI TX Data worker thread ---- */
 
 static void nci_tx_work(struct work_struct *work)
@@ -1516,7 +1529,7 @@ 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)) {
+		if (!nci_valid_size(skb)) {
 			kfree_skb(skb);
 			kcov_remote_stop();
 			break;