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Message-ID: <20240428134525.GW516117@kernel.org>
Date: Sun, 28 Apr 2024 14:45:25 +0100
From: Simon Horman <horms@...nel.org>
To: Ryosuke Yasuoka <ryasuoka@...hat.com>
Cc: krzk@...nel.org, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org, syoshida@...hat.com,
syzbot+d7b4dc6cd50410152534@...kaller.appspotmail.com
Subject: Re: [PATCH net v2] nfc: nci: Fix uninit-value in nci_rx_work
On Sat, Apr 27, 2024 at 07:35:54PM +0900, Ryosuke Yasuoka wrote:
> 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>
..
> @@ -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;
Hi Yasuoka-san,
My reading is that this will jump to the label invalid_pkt_free,
which is intended.
> nci_rsp_packet(ndev, skb);
> break;
But this will exit the switch statement, which lands
at the label invalid_pkt_free, where skb is kfreed.
This doesn't seem to be intended.
>
> 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;
> }
If so, then one solution may be to add the following here:
continue;
> +invalid_pkt_free:
> + kfree_skb(skb);
> + break;
> }
>
> /* check if a data exchange timeout has occurred */
> --
> 2.44.0
>
>
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