From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/input/tablet/acecad.c | 254 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 254 insertions(+) create mode 100644 drivers/input/tablet/acecad.c (limited to 'drivers/input/tablet/acecad.c') diff --git a/drivers/input/tablet/acecad.c b/drivers/input/tablet/acecad.c new file mode 100644 index 000000000..ba79dff21 --- /dev/null +++ b/drivers/input/tablet/acecad.c @@ -0,0 +1,254 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2001-2005 Edouard TISSERANT + * Copyright (c) 2004-2005 Stephane VOLTZ + * + * USB Acecad "Acecad Flair" tablet support + * + * Changelog: + * v3.2 - Added sysfs support + */ + +#include +#include +#include +#include + +MODULE_AUTHOR("Edouard TISSERANT "); +MODULE_DESCRIPTION("USB Acecad Flair tablet driver"); +MODULE_LICENSE("GPL"); + +#define USB_VENDOR_ID_ACECAD 0x0460 +#define USB_DEVICE_ID_FLAIR 0x0004 +#define USB_DEVICE_ID_302 0x0008 + +struct usb_acecad { + char name[128]; + char phys[64]; + struct usb_interface *intf; + struct input_dev *input; + struct urb *irq; + + unsigned char *data; + dma_addr_t data_dma; +}; + +static void usb_acecad_irq(struct urb *urb) +{ + struct usb_acecad *acecad = urb->context; + unsigned char *data = acecad->data; + struct input_dev *dev = acecad->input; + struct usb_interface *intf = acecad->intf; + struct usb_device *udev = interface_to_usbdev(intf); + int prox, status; + + switch (urb->status) { + case 0: + /* success */ + break; + case -ECONNRESET: + case -ENOENT: + case -ESHUTDOWN: + /* this urb is terminated, clean up */ + dev_dbg(&intf->dev, "%s - urb shutting down with status: %d\n", + __func__, urb->status); + return; + default: + dev_dbg(&intf->dev, "%s - nonzero urb status received: %d\n", + __func__, urb->status); + goto resubmit; + } + + prox = (data[0] & 0x04) >> 2; + input_report_key(dev, BTN_TOOL_PEN, prox); + + if (prox) { + int x = data[1] | (data[2] << 8); + int y = data[3] | (data[4] << 8); + /* Pressure should compute the same way for flair and 302 */ + int pressure = data[5] | (data[6] << 8); + int touch = data[0] & 0x01; + int stylus = (data[0] & 0x10) >> 4; + int stylus2 = (data[0] & 0x20) >> 5; + input_report_abs(dev, ABS_X, x); + input_report_abs(dev, ABS_Y, y); + input_report_abs(dev, ABS_PRESSURE, pressure); + input_report_key(dev, BTN_TOUCH, touch); + input_report_key(dev, BTN_STYLUS, stylus); + input_report_key(dev, BTN_STYLUS2, stylus2); + } + + /* event termination */ + input_sync(dev); + +resubmit: + status = usb_submit_urb(urb, GFP_ATOMIC); + if (status) + dev_err(&intf->dev, + "can't resubmit intr, %s-%s/input0, status %d\n", + udev->bus->bus_name, + udev->devpath, status); +} + +static int usb_acecad_open(struct input_dev *dev) +{ + struct usb_acecad *acecad = input_get_drvdata(dev); + + acecad->irq->dev = interface_to_usbdev(acecad->intf); + if (usb_submit_urb(acecad->irq, GFP_KERNEL)) + return -EIO; + + return 0; +} + +static void usb_acecad_close(struct input_dev *dev) +{ + struct usb_acecad *acecad = input_get_drvdata(dev); + + usb_kill_urb(acecad->irq); +} + +static int usb_acecad_probe(struct usb_interface *intf, const struct usb_device_id *id) +{ + struct usb_device *dev = interface_to_usbdev(intf); + struct usb_host_interface *interface = intf->cur_altsetting; + struct usb_endpoint_descriptor *endpoint; + struct usb_acecad *acecad; + struct input_dev *input_dev; + int pipe, maxp; + int err; + + if (interface->desc.bNumEndpoints != 1) + return -ENODEV; + + endpoint = &interface->endpoint[0].desc; + + if (!usb_endpoint_is_int_in(endpoint)) + return -ENODEV; + + pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress); + maxp = usb_maxpacket(dev, pipe); + + acecad = kzalloc_obj(*acecad); + input_dev = input_allocate_device(); + if (!acecad || !input_dev) { + err = -ENOMEM; + goto fail1; + } + + acecad->data = usb_alloc_coherent(dev, 8, GFP_KERNEL, &acecad->data_dma); + if (!acecad->data) { + err= -ENOMEM; + goto fail1; + } + + acecad->irq = usb_alloc_urb(0, GFP_KERNEL); + if (!acecad->irq) { + err = -ENOMEM; + goto fail2; + } + + acecad->intf = intf; + acecad->input = input_dev; + + if (dev->manufacturer) + strscpy(acecad->name, dev->manufacturer, sizeof(acecad->name)); + + if (dev->product) { + if (dev->manufacturer) + strlcat(acecad->name, " ", sizeof(acecad->name)); + strlcat(acecad->name, dev->product, sizeof(acecad->name)); + } + + usb_make_path(dev, acecad->phys, sizeof(acecad->phys)); + strlcat(acecad->phys, "/input0", sizeof(acecad->phys)); + + input_dev->name = acecad->name; + input_dev->phys = acecad->phys; + usb_to_input_id(dev, &input_dev->id); + input_dev->dev.parent = &intf->dev; + + input_set_drvdata(input_dev, acecad); + + input_dev->open = usb_acecad_open; + input_dev->close = usb_acecad_close; + + input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); + input_dev->keybit[BIT_WORD(BTN_DIGI)] = BIT_MASK(BTN_TOOL_PEN) | + BIT_MASK(BTN_TOUCH) | BIT_MASK(BTN_STYLUS) | + BIT_MASK(BTN_STYLUS2); + + switch (id->driver_info) { + case 0: + input_set_abs_params(input_dev, ABS_X, 0, 5000, 4, 0); + input_set_abs_params(input_dev, ABS_Y, 0, 3750, 4, 0); + input_set_abs_params(input_dev, ABS_PRESSURE, 0, 512, 0, 0); + if (!strlen(acecad->name)) + snprintf(acecad->name, sizeof(acecad->name), + "USB Acecad Flair Tablet %04x:%04x", + le16_to_cpu(dev->descriptor.idVendor), + le16_to_cpu(dev->descriptor.idProduct)); + break; + + case 1: + input_set_abs_params(input_dev, ABS_X, 0, 53000, 4, 0); + input_set_abs_params(input_dev, ABS_Y, 0, 2250, 4, 0); + input_set_abs_params(input_dev, ABS_PRESSURE, 0, 1024, 0, 0); + if (!strlen(acecad->name)) + snprintf(acecad->name, sizeof(acecad->name), + "USB Acecad 302 Tablet %04x:%04x", + le16_to_cpu(dev->descriptor.idVendor), + le16_to_cpu(dev->descriptor.idProduct)); + break; + } + + usb_fill_int_urb(acecad->irq, dev, pipe, + acecad->data, maxp > 8 ? 8 : maxp, + usb_acecad_irq, acecad, endpoint->bInterval); + acecad->irq->transfer_dma = acecad->data_dma; + acecad->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP; + + err = input_register_device(acecad->input); + if (err) + goto fail3; + + usb_set_intfdata(intf, acecad); + + return 0; + + fail3: usb_free_urb(acecad->irq); + fail2: usb_free_coherent(dev, 8, acecad->data, acecad->data_dma); + fail1: input_free_device(input_dev); + kfree(acecad); + return err; +} + +static void usb_acecad_disconnect(struct usb_interface *intf) +{ + struct usb_acecad *acecad = usb_get_intfdata(intf); + struct usb_device *udev = interface_to_usbdev(intf); + + usb_set_intfdata(intf, NULL); + + input_unregister_device(acecad->input); + usb_free_urb(acecad->irq); + usb_free_coherent(udev, 8, acecad->data, acecad->data_dma); + kfree(acecad); +} + +static const struct usb_device_id usb_acecad_id_table[] = { + { USB_DEVICE(USB_VENDOR_ID_ACECAD, USB_DEVICE_ID_FLAIR), .driver_info = 0 }, + { USB_DEVICE(USB_VENDOR_ID_ACECAD, USB_DEVICE_ID_302), .driver_info = 1 }, + { } +}; + +MODULE_DEVICE_TABLE(usb, usb_acecad_id_table); + +static struct usb_driver usb_acecad_driver = { + .name = "usb_acecad", + .probe = usb_acecad_probe, + .disconnect = usb_acecad_disconnect, + .id_table = usb_acecad_id_table, +}; + +module_usb_driver(usb_acecad_driver); -- cgit v1.3.1