x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 438 insertions, 0 deletions

diff --git a/drivers/net/usb/cdc-phonet.c b/drivers/net/usb/cdc-phonet.c
new file mode 100644
index 000000000..165650ece
--- /dev/null
+++ b/drivers/net/usb/cdc-phonet.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * phonet.c -- USB CDC Phonet host driver
+ *
+ * Copyright (C) 2008-2009 Nokia Corporation. All rights reserved.
+ *
+ * Author: Rémi Denis-Courmont
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/gfp.h>
+#include <linux/usb.h>
+#include <linux/usb/cdc.h>
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/if_phonet.h>
+#include <linux/phonet.h>
+
+#define PN_MEDIA_USB	0x1B
+
+static const unsigned rxq_size = 17;
+
+struct usbpn_dev {
+	struct net_device	*dev;
+
+	struct usb_interface	*intf, *data_intf;
+	struct usb_device	*usb;
+	unsigned int		tx_pipe, rx_pipe;
+	u8 active_setting;
+	u8 disconnected;
+
+	unsigned		tx_queue;
+	spinlock_t		tx_lock;
+
+	spinlock_t		rx_lock;
+	struct sk_buff		*rx_skb;
+	struct urb		*urbs[];
+};
+
+static void tx_complete(struct urb *req);
+static void rx_complete(struct urb *req);
+
+/*
+ * Network device callbacks
+ */
+static netdev_tx_t usbpn_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct usbpn_dev *pnd = netdev_priv(dev);
+	struct urb *req = NULL;
+	unsigned long flags;
+	int err;
+
+	if (skb->protocol != htons(ETH_P_PHONET))
+		goto drop;
+
+	req = usb_alloc_urb(0, GFP_ATOMIC);
+	if (!req)
+		goto drop;
+	usb_fill_bulk_urb(req, pnd->usb, pnd->tx_pipe, skb->data, skb->len,
+				tx_complete, skb);
+	req->transfer_flags = URB_ZERO_PACKET;
+	err = usb_submit_urb(req, GFP_ATOMIC);
+	if (err) {
+		usb_free_urb(req);
+		goto drop;
+	}
+
+	spin_lock_irqsave(&pnd->tx_lock, flags);
+	pnd->tx_queue++;
+	if (pnd->tx_queue >= dev->tx_queue_len)
+		netif_stop_queue(dev);
+	spin_unlock_irqrestore(&pnd->tx_lock, flags);
+	return NETDEV_TX_OK;
+
+drop:
+	dev_kfree_skb(skb);
+	dev->stats.tx_dropped++;
+	return NETDEV_TX_OK;
+}
+
+static void tx_complete(struct urb *req)
+{
+	struct sk_buff *skb = req->context;
+	struct net_device *dev = skb->dev;
+	struct usbpn_dev *pnd = netdev_priv(dev);
+	int status = req->status;
+	unsigned long flags;
+
+	switch (status) {
+	case 0:
+		dev->stats.tx_bytes += skb->len;
+		break;
+
+	case -ENOENT:
+	case -ECONNRESET:
+	case -ESHUTDOWN:
+		dev->stats.tx_aborted_errors++;
+		fallthrough;
+	default:
+		dev->stats.tx_errors++;
+		dev_dbg(&dev->dev, "TX error (%d)\n", status);
+	}
+	dev->stats.tx_packets++;
+
+	spin_lock_irqsave(&pnd->tx_lock, flags);
+	pnd->tx_queue--;
+	netif_wake_queue(dev);
+	spin_unlock_irqrestore(&pnd->tx_lock, flags);
+
+	dev_kfree_skb_any(skb);
+	usb_free_urb(req);
+}
+
+static int rx_submit(struct usbpn_dev *pnd, struct urb *req, gfp_t gfp_flags)
+{
+	struct net_device *dev = pnd->dev;
+	struct page *page;
+	int err;
+
+	page = __dev_alloc_page(gfp_flags | __GFP_NOMEMALLOC);
+	if (!page)
+		return -ENOMEM;
+
+	usb_fill_bulk_urb(req, pnd->usb, pnd->rx_pipe, page_address(page),
+				PAGE_SIZE, rx_complete, dev);
+	req->transfer_flags = 0;
+	err = usb_submit_urb(req, gfp_flags);
+	if (unlikely(err)) {
+		dev_dbg(&dev->dev, "RX submit error (%d)\n", err);
+		put_page(page);
+	}
+	return err;
+}
+
+static void rx_complete(struct urb *req)
+{
+	struct net_device *dev = req->context;
+	struct usbpn_dev *pnd = netdev_priv(dev);
+	struct page *page = virt_to_page(req->transfer_buffer);
+	struct sk_buff *skb;
+	unsigned long flags;
+	int status = req->status;
+
+	switch (status) {
+	case 0:
+		spin_lock_irqsave(&pnd->rx_lock, flags);
+		skb = pnd->rx_skb;
+		if (!skb) {
+			skb = pnd->rx_skb = netdev_alloc_skb(dev, 12);
+			if (likely(skb)) {
+				/* Can't use pskb_pull() on page in IRQ */
+				skb_put_data(skb, page_address(page), 1);
+				skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
+						page, 1, req->actual_length,
+						PAGE_SIZE);
+				page = NULL;
+			}
+		} else if (skb_shinfo(skb)->nr_frags < MAX_SKB_FRAGS) {
+			skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
+					page, 0, req->actual_length,
+					PAGE_SIZE);
+			page = NULL;
+		} else {
+			dev_kfree_skb_any(skb);
+			pnd->rx_skb = NULL;
+			skb = NULL;
+			dev->stats.rx_length_errors++;
+		}
+		if (req->actual_length < PAGE_SIZE)
+			pnd->rx_skb = NULL; /* Last fragment */
+		else
+			skb = NULL;
+		spin_unlock_irqrestore(&pnd->rx_lock, flags);
+		if (skb) {
+			skb->protocol = htons(ETH_P_PHONET);
+			skb_reset_mac_header(skb);
+			__skb_pull(skb, 1);
+			skb->dev = dev;
+			dev->stats.rx_packets++;
+			dev->stats.rx_bytes += skb->len;
+
+			netif_rx(skb);
+		}
+		goto resubmit;
+
+	case -ENOENT:
+	case -ECONNRESET:
+	case -ESHUTDOWN:
+		req = NULL;
+		break;
+
+	case -EOVERFLOW:
+		dev->stats.rx_over_errors++;
+		dev_dbg(&dev->dev, "RX overflow\n");
+		break;
+
+	case -EILSEQ:
+		dev->stats.rx_crc_errors++;
+		break;
+	}
+
+	dev->stats.rx_errors++;
+resubmit:
+	if (page)
+		put_page(page);
+	if (req)
+		rx_submit(pnd, req, GFP_ATOMIC);
+}
+
+static int usbpn_close(struct net_device *dev);
+
+static int usbpn_open(struct net_device *dev)
+{
+	struct usbpn_dev *pnd = netdev_priv(dev);
+	int err;
+	unsigned i;
+	unsigned num = pnd->data_intf->cur_altsetting->desc.bInterfaceNumber;
+
+	err = usb_set_interface(pnd->usb, num, pnd->active_setting);
+	if (err)
+		return err;
+
+	for (i = 0; i < rxq_size; i++) {
+		struct urb *req = usb_alloc_urb(0, GFP_KERNEL);
+
+		if (!req || rx_submit(pnd, req, GFP_KERNEL)) {
+			usb_free_urb(req);
+			usbpn_close(dev);
+			return -ENOMEM;
+		}
+		pnd->urbs[i] = req;
+	}
+
+	netif_wake_queue(dev);
+	return 0;
+}
+
+static int usbpn_close(struct net_device *dev)
+{
+	struct usbpn_dev *pnd = netdev_priv(dev);
+	unsigned i;
+	unsigned num = pnd->data_intf->cur_altsetting->desc.bInterfaceNumber;
+
+	netif_stop_queue(dev);
+
+	for (i = 0; i < rxq_size; i++) {
+		struct urb *req = pnd->urbs[i];
+
+		if (!req)
+			continue;
+		usb_kill_urb(req);
+		usb_free_urb(req);
+		pnd->urbs[i] = NULL;
+	}
+
+	return usb_set_interface(pnd->usb, num, !pnd->active_setting);
+}
+
+static int usbpn_siocdevprivate(struct net_device *dev, struct ifreq *ifr,
+				void __user *data, int cmd)
+{
+	struct if_phonet_req *req = (struct if_phonet_req *)ifr;
+
+	switch (cmd) {
+	case SIOCPNGAUTOCONF:
+		req->ifr_phonet_autoconf.device = PN_DEV_PC;
+		return 0;
+	}
+	return -ENOIOCTLCMD;
+}
+
+static const struct net_device_ops usbpn_ops = {
+	.ndo_open	= usbpn_open,
+	.ndo_stop	= usbpn_close,
+	.ndo_start_xmit = usbpn_xmit,
+	.ndo_siocdevprivate = usbpn_siocdevprivate,
+};
+
+static void usbpn_setup(struct net_device *dev)
+{
+	const u8 addr = PN_MEDIA_USB;
+
+	dev->features		= 0;
+	dev->netdev_ops		= &usbpn_ops;
+	dev->header_ops		= &phonet_header_ops;
+	dev->type		= ARPHRD_PHONET;
+	dev->flags		= IFF_POINTOPOINT | IFF_NOARP;
+	dev->mtu		= PHONET_MAX_MTU;
+	dev->min_mtu		= PHONET_MIN_MTU;
+	dev->max_mtu		= PHONET_MAX_MTU;
+	dev->hard_header_len	= 1;
+	dev->addr_len		= 1;
+	dev_addr_set(dev, &addr);
+	dev->tx_queue_len	= 3;
+
+	dev->needs_free_netdev	= true;
+}
+
+/*
+ * USB driver callbacks
+ */
+static const struct usb_device_id usbpn_ids[] = {
+	{
+		.match_flags = USB_DEVICE_ID_MATCH_VENDOR
+			| USB_DEVICE_ID_MATCH_INT_CLASS
+			| USB_DEVICE_ID_MATCH_INT_SUBCLASS,
+		.idVendor = 0x0421, /* Nokia */
+		.bInterfaceClass = USB_CLASS_COMM,
+		.bInterfaceSubClass = 0xFE,
+	},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(usb, usbpn_ids);
+
+static struct usb_driver usbpn_driver;
+
+static int usbpn_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	static const char ifname[] = "usbpn%d";
+	const struct usb_cdc_union_desc *union_header = NULL;
+	const struct usb_host_interface *data_desc;
+	struct usb_interface *data_intf;
+	struct usb_device *usbdev = interface_to_usbdev(intf);
+	struct net_device *dev;
+	struct usbpn_dev *pnd;
+	u8 *data;
+	int phonet = 0;
+	int len, err;
+	struct usb_cdc_parsed_header hdr;
+
+	data = intf->altsetting->extra;
+	len = intf->altsetting->extralen;
+	cdc_parse_cdc_header(&hdr, intf, data, len);
+	union_header = hdr.usb_cdc_union_desc;
+	phonet = hdr.phonet_magic_present;
+
+	if (!union_header || !phonet)
+		return -EINVAL;
+
+	data_intf = usb_ifnum_to_if(usbdev, union_header->bSlaveInterface0);
+	if (data_intf == NULL)
+		return -ENODEV;
+	/* Data interface has one inactive and one active setting */
+	if (data_intf->num_altsetting != 2)
+		return -EINVAL;
+	if (data_intf->altsetting[0].desc.bNumEndpoints == 0 &&
+	    data_intf->altsetting[1].desc.bNumEndpoints == 2)
+		data_desc = data_intf->altsetting + 1;
+	else
+	if (data_intf->altsetting[0].desc.bNumEndpoints == 2 &&
+	    data_intf->altsetting[1].desc.bNumEndpoints == 0)
+		data_desc = data_intf->altsetting;
+	else
+		return -EINVAL;
+
+	dev = alloc_netdev(struct_size(pnd, urbs, rxq_size), ifname,
+			   NET_NAME_UNKNOWN, usbpn_setup);
+	if (!dev)
+		return -ENOMEM;
+
+	pnd = netdev_priv(dev);
+	SET_NETDEV_DEV(dev, &intf->dev);
+
+	pnd->dev = dev;
+	pnd->usb = usbdev;
+	pnd->intf = intf;
+	pnd->data_intf = data_intf;
+	spin_lock_init(&pnd->tx_lock);
+	spin_lock_init(&pnd->rx_lock);
+	/* Endpoints */
+	if (usb_pipein(data_desc->endpoint[0].desc.bEndpointAddress)) {
+		pnd->rx_pipe = usb_rcvbulkpipe(usbdev,
+			data_desc->endpoint[0].desc.bEndpointAddress);
+		pnd->tx_pipe = usb_sndbulkpipe(usbdev,
+			data_desc->endpoint[1].desc.bEndpointAddress);
+	} else {
+		pnd->rx_pipe = usb_rcvbulkpipe(usbdev,
+			data_desc->endpoint[1].desc.bEndpointAddress);
+		pnd->tx_pipe = usb_sndbulkpipe(usbdev,
+			data_desc->endpoint[0].desc.bEndpointAddress);
+	}
+	pnd->active_setting = data_desc - data_intf->altsetting;
+
+	err = usb_driver_claim_interface(&usbpn_driver, data_intf, pnd);
+	if (err)
+		goto out;
+
+	/* Force inactive mode until the network device is brought UP */
+	usb_set_interface(usbdev, union_header->bSlaveInterface0,
+				!pnd->active_setting);
+	usb_set_intfdata(intf, pnd);
+
+	err = register_netdev(dev);
+	if (err) {
+		/* Set disconnected flag so that disconnect() returns early. */
+		pnd->disconnected = 1;
+		usb_driver_release_interface(&usbpn_driver, data_intf);
+		goto out;
+	}
+
+	dev_dbg(&dev->dev, "USB CDC Phonet device found\n");
+	return 0;
+
+out:
+	usb_set_intfdata(intf, NULL);
+	free_netdev(dev);
+	return err;
+}
+
+static void usbpn_disconnect(struct usb_interface *intf)
+{
+	struct usbpn_dev *pnd = usb_get_intfdata(intf);
+
+	if (pnd->disconnected)
+		return;
+
+	pnd->disconnected = 1;
+	usb_driver_release_interface(&usbpn_driver,
+			(pnd->intf == intf) ? pnd->data_intf : pnd->intf);
+	unregister_netdev(pnd->dev);
+}
+
+static struct usb_driver usbpn_driver = {
+	.name =		"cdc_phonet",
+	.probe =	usbpn_probe,
+	.disconnect =	usbpn_disconnect,
+	.id_table =	usbpn_ids,
+	.disable_hub_initiated_lpm = 1,
+};
+
+module_usb_driver(usbpn_driver);
+
+MODULE_AUTHOR("Remi Denis-Courmont");
+MODULE_DESCRIPTION("USB CDC Phonet host interface");
+MODULE_LICENSE("GPL");