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Subject[PATCH net v4] nfc: nci: Fix uninit-value in nci_rx_work
Date
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>
---
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

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