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, 216 insertions, 0 deletions

diff --git a/drivers/comedi/comedi_pci.c b/drivers/comedi/comedi_pci.c
new file mode 100644
index 000000000..da618f5e3
--- /dev/null
+++ b/drivers/comedi/comedi_pci.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * comedi_pci.c
+ * Comedi PCI driver specific functions.
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/comedi/comedi_pci.h>
+
+/**
+ * comedi_to_pci_dev() - Return PCI device attached to COMEDI device
+ * @dev: COMEDI device.
+ *
+ * Assuming @dev->hw_dev is non-%NULL, it is assumed to be pointing to a
+ * a &struct device embedded in a &struct pci_dev.
+ *
+ * Return: Attached PCI device if @dev->hw_dev is non-%NULL.
+ * Return %NULL if @dev->hw_dev is %NULL.
+ */
+struct pci_dev *comedi_to_pci_dev(struct comedi_device *dev)
+{
+	return dev->hw_dev ? to_pci_dev(dev->hw_dev) : NULL;
+}
+EXPORT_SYMBOL_GPL(comedi_to_pci_dev);
+
+/**
+ * comedi_pci_enable() - Enable the PCI device and request the regions
+ * @dev: COMEDI device.
+ *
+ * Assuming @dev->hw_dev is non-%NULL, it is assumed to be pointing to a
+ * a &struct device embedded in a &struct pci_dev.  Enable the PCI device
+ * and request its regions.  Set @dev->ioenabled to %true if successful,
+ * otherwise undo what was done.
+ *
+ * Calls to comedi_pci_enable() and comedi_pci_disable() cannot be nested.
+ *
+ * Return:
+ *	0 on success,
+ *	-%ENODEV if @dev->hw_dev is %NULL,
+ *	-%EBUSY if regions busy,
+ *	or some negative error number if failed to enable PCI device.
+ *
+ */
+int comedi_pci_enable(struct comedi_device *dev)
+{
+	struct pci_dev *pcidev = comedi_to_pci_dev(dev);
+	int rc;
+
+	if (!pcidev)
+		return -ENODEV;
+
+	rc = pci_enable_device(pcidev);
+	if (rc < 0)
+		return rc;
+
+	rc = pci_request_regions(pcidev, dev->board_name);
+	if (rc < 0)
+		pci_disable_device(pcidev);
+	else
+		dev->ioenabled = true;
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(comedi_pci_enable);
+
+/**
+ * comedi_pci_disable() - Release the regions and disable the PCI device
+ * @dev: COMEDI device.
+ *
+ * Assuming @dev->hw_dev is non-%NULL, it is assumed to be pointing to a
+ * a &struct device embedded in a &struct pci_dev.  If the earlier call
+ * to comedi_pci_enable() was successful, release the PCI device's regions
+ * and disable it.  Reset @dev->ioenabled back to %false.
+ */
+void comedi_pci_disable(struct comedi_device *dev)
+{
+	struct pci_dev *pcidev = comedi_to_pci_dev(dev);
+
+	if (pcidev && dev->ioenabled) {
+		pci_release_regions(pcidev);
+		pci_disable_device(pcidev);
+	}
+	dev->ioenabled = false;
+}
+EXPORT_SYMBOL_GPL(comedi_pci_disable);
+
+/**
+ * comedi_pci_detach() - A generic "detach" handler for PCI COMEDI drivers
+ * @dev: COMEDI device.
+ *
+ * COMEDI drivers for PCI devices that need no special clean-up of private data
+ * and have no ioremapped regions other than that pointed to by @dev->mmio may
+ * use this function as its "detach" handler called by the COMEDI core when a
+ * COMEDI device is being detached from the low-level driver.  It may be also
+ * called from a more specific "detach" handler that does additional clean-up.
+ *
+ * Free the IRQ if @dev->irq is non-zero, iounmap @dev->mmio if it is
+ * non-%NULL, and call comedi_pci_disable() to release the PCI device's regions
+ * and disable it.
+ */
+void comedi_pci_detach(struct comedi_device *dev)
+{
+	struct pci_dev *pcidev = comedi_to_pci_dev(dev);
+
+	if (!pcidev || !dev->ioenabled)
+		return;
+
+	if (dev->irq) {
+		free_irq(dev->irq, dev);
+		dev->irq = 0;
+	}
+	if (dev->mmio) {
+		iounmap(dev->mmio);
+		dev->mmio = NULL;
+	}
+	comedi_pci_disable(dev);
+}
+EXPORT_SYMBOL_GPL(comedi_pci_detach);
+
+/**
+ * comedi_pci_auto_config() - Configure/probe a PCI COMEDI device
+ * @pcidev: PCI device.
+ * @driver: Registered COMEDI driver.
+ * @context: Driver specific data, passed to comedi_auto_config().
+ *
+ * Typically called from the pci_driver (*probe) function.  Auto-configure
+ * a COMEDI device, using the &struct device embedded in *@pcidev as the
+ * hardware device.  The @context value gets passed through to @driver's
+ * "auto_attach" handler.  The "auto_attach" handler may call
+ * comedi_to_pci_dev() on the passed in COMEDI device to recover @pcidev.
+ *
+ * Return: The result of calling comedi_auto_config() (0 on success, or
+ * a negative error number on failure).
+ */
+int comedi_pci_auto_config(struct pci_dev *pcidev,
+			   struct comedi_driver *driver,
+			   unsigned long context)
+{
+	return comedi_auto_config(&pcidev->dev, driver, context);
+}
+EXPORT_SYMBOL_GPL(comedi_pci_auto_config);
+
+/**
+ * comedi_pci_auto_unconfig() - Unconfigure/remove a PCI COMEDI device
+ * @pcidev: PCI device.
+ *
+ * Typically called from the pci_driver (*remove) function.  Auto-unconfigure
+ * a COMEDI device attached to this PCI device, using a pointer to the
+ * &struct device embedded in *@pcidev as the hardware device.  The COMEDI
+ * driver's "detach" handler will be called during unconfiguration of the
+ * COMEDI device.
+ *
+ * Note that the COMEDI device may have already been unconfigured using the
+ * %COMEDI_DEVCONFIG ioctl, in which case this attempt to unconfigure it
+ * again should be ignored.
+ */
+void comedi_pci_auto_unconfig(struct pci_dev *pcidev)
+{
+	comedi_auto_unconfig(&pcidev->dev);
+}
+EXPORT_SYMBOL_GPL(comedi_pci_auto_unconfig);
+
+/**
+ * comedi_pci_driver_register() - Register a PCI COMEDI driver
+ * @comedi_driver: COMEDI driver to be registered.
+ * @pci_driver: PCI driver to be registered.
+ *
+ * This function is called from the module_init() of PCI COMEDI driver modules
+ * to register the COMEDI driver and the PCI driver.  Do not call it directly,
+ * use the module_comedi_pci_driver() helper macro instead.
+ *
+ * Return: 0 on success, or a negative error number on failure.
+ */
+int comedi_pci_driver_register(struct comedi_driver *comedi_driver,
+			       struct pci_driver *pci_driver)
+{
+	int ret;
+
+	ret = comedi_driver_register(comedi_driver);
+	if (ret < 0)
+		return ret;
+
+	ret = pci_register_driver(pci_driver);
+	if (ret < 0) {
+		comedi_driver_unregister(comedi_driver);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(comedi_pci_driver_register);
+
+/**
+ * comedi_pci_driver_unregister() - Unregister a PCI COMEDI driver
+ * @comedi_driver: COMEDI driver to be unregistered.
+ * @pci_driver: PCI driver to be unregistered.
+ *
+ * This function is called from the module_exit() of PCI COMEDI driver modules
+ * to unregister the PCI driver and the COMEDI driver.  Do not call it
+ * directly, use the module_comedi_pci_driver() helper macro instead.
+ */
+void comedi_pci_driver_unregister(struct comedi_driver *comedi_driver,
+				  struct pci_driver *pci_driver)
+{
+	pci_unregister_driver(pci_driver);
+	comedi_driver_unregister(comedi_driver);
+}
+EXPORT_SYMBOL_GPL(comedi_pci_driver_unregister);
+
+MODULE_AUTHOR("https://www.comedi.org");
+MODULE_DESCRIPTION("Comedi PCI interface module");
+MODULE_LICENSE("GPL");