linux-kernel - [PATCH net v4] nfc: nci: Fix uninit-value in nci_rx

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Date: Thu,  9 May 2024 20:30:33 +0900
From: Ryosuke Yasuoka <ryasuoka@...hat.com>
To: krzk@...nel.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org
Cc: Ryosuke Yasuoka <ryasuoka@...hat.com>,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	syoshida@...hat.com,
	syzbot+d7b4dc6cd50410152534@...kaller.appspotmail.com
Subject: [PATCH net v4] nfc: nci: Fix uninit-value in nci_rx_work

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@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d7b4dc6cd50410152534 [1]
Signed-off-by: Ryosuke Yasuoka <ryasuoka@...hat.com>
---
v4
- v3 patch uses goto statement and it makes codes complicated. So this
  patch simply calls kfree_skb inside loop and remove goto statement.
- [2] inserted kcov_remote_stop() to fix kcov check. However, as we
  discuss about my v3 patch [3], it should not exit the for statement
  and should continue processing subsequent packets. This patch removes
  them and simply insert continue statement.

[2] https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=19e35f24750d

v3
https://lore.kernel.org/netdev/20240502082323.250739-1-ryasuoka@redhat.com/T/
- 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. [3]

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 | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c
index b133dc55304c..0aaff30cb68f 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)
@@ -1516,24 +1526,32 @@ 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 (!skb->len) {
 			kfree_skb(skb);
-			kcov_remote_stop();
-			break;
+			continue;
 		}
 
 		/* Process frame */
 		switch (nci_mt(skb->data)) {
 		case NCI_MT_RSP_PKT:
-			nci_rsp_packet(ndev, skb);
+			if (nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
+				nci_rsp_packet(ndev, skb);
+			else
+				kfree_skb(skb);
 			break;
 
 		case NCI_MT_NTF_PKT:
-			nci_ntf_packet(ndev, skb);
+			if (nci_valid_size(skb, NCI_CTRL_HDR_SIZE))
+				nci_ntf_packet(ndev, skb);
+			else
+				kfree_skb(skb);
 			break;
 
 		case NCI_MT_DATA_PKT:
-			nci_rx_data_packet(ndev, skb);
+			if (nci_valid_size(skb, NCI_DATA_HDR_SIZE))
+				nci_rx_data_packet(ndev, skb);
+			else
+				kfree_skb(skb);
 			break;
 
 		default:
-- 
2.44.0