[PATCH net v3] nfc: nci: Fix uninit-value in nci_rx_work

[Ryosuke Yasuoka <ryasuoka@redhat.com>]

syzbot reported the following uninit-value access issue [1]

nci_rx_work() parses received packet from ndev->rx_q. It should be
validated header size, payload size and total packet size before
processing the packet. If an invalid packet is detected, it should be
silently discarded.

Fixes: d24b03535e5e ("nfc: nci: Fix uninit-value in nci_dev_up and nci_ntf_packet")
Reported-and-tested-by: syzbot+d7b4dc6cd50410152534@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d7b4dc6cd50410152534 [1]
Signed-off-by: Ryosuke Yasuoka <ryasuoka@redhat.com>
---

v3
- As Simon pointed out, the valid packets will reach invalid_pkt_free
and kfree_skb(skb) after being handled correctly in switch statement.
It can lead to double free issues, which is not intended. So this patch
uses "continue" instead of "break" in switch statement.

- In the current implementation, once zero payload size is detected, the
for statement exits. It should continue processing subsequent packets. 
So this patch just frees skb in invalid_pkt_free when the invalid 
packets are detected.

v2
https://lore.kernel.org/lkml/20240428134525.GW516117@kernel.org/T/

- The v1 patch only checked whether skb->len is zero. This patch also
  checks header size, payload size and total packet size.


v1
https://lore.kernel.org/linux-kernel/CANn89iJrQevxPFLCj2P=U+XSisYD0jqrUQpa=zWMXTjj5+RriA@mail.gmail.com/T/


 net/nfc/nci/core.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index 0d26c8ec9993..e4f92a090022 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 +1526,35 @@ 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;
+			continue;
 
 		case NCI_MT_NTF_PKT:
+			if (!nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
+				goto invalid_pkt_free;
 			nci_ntf_packet(ndev, skb);
-			break;
+			continue;
 
 		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;
+			continue;
 
 		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);
 	}
 
 	/* check if a data exchange timeout has occurred */
-- 
2.44.0