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

3 files changed, 658 insertions, 0 deletions

diff --git a/drivers/misc/uacce/Kconfig b/drivers/misc/uacce/Kconfig
new file mode 100644
index 000000000..5e39b6083
--- /dev/null
+++ b/drivers/misc/uacce/Kconfig
@@ -0,0 +1,13 @@
+config UACCE
+	tristate "Accelerator Framework for User Land"
+	depends on IOMMU_API
+	help
+	  UACCE provides interface for the user process to access the hardware
+	  without interaction with the kernel space in data path.
+
+	  The user-space interface is described in
+	  include/uapi/misc/uacce/uacce.h
+
+	  See Documentation/misc-devices/uacce.rst for more details.
+
+	  If you don't know what to do here, say N.
diff --git a/drivers/misc/uacce/Makefile b/drivers/misc/uacce/Makefile
new file mode 100644
index 000000000..5b4374e8b
--- /dev/null
+++ b/drivers/misc/uacce/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+obj-$(CONFIG_UACCE) += uacce.o
diff --git a/drivers/misc/uacce/uacce.c b/drivers/misc/uacce/uacce.c
new file mode 100644
index 000000000..45521d4a5
--- /dev/null
+++ b/drivers/misc/uacce/uacce.c
@@ -0,0 +1,643 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/compat.h>
+#include <linux/dma-mapping.h>
+#include <linux/iommu.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/uacce.h>
+
+static dev_t uacce_devt;
+static DEFINE_XARRAY_ALLOC(uacce_xa);
+
+static const struct class uacce_class = {
+	.name = UACCE_NAME,
+};
+
+/*
+ * If the parent driver or the device disappears, the queue state is invalid and
+ * ops are not usable anymore.
+ */
+static bool uacce_queue_is_valid(struct uacce_queue *q)
+{
+	return q->state == UACCE_Q_INIT || q->state == UACCE_Q_STARTED;
+}
+
+static int uacce_start_queue(struct uacce_queue *q)
+{
+	int ret;
+
+	if (q->state != UACCE_Q_INIT)
+		return -EINVAL;
+
+	if (q->uacce->ops->start_queue) {
+		ret = q->uacce->ops->start_queue(q);
+		if (ret < 0)
+			return ret;
+	}
+
+	q->state = UACCE_Q_STARTED;
+	return 0;
+}
+
+static int uacce_stop_queue(struct uacce_queue *q)
+{
+	struct uacce_device *uacce = q->uacce;
+
+	if (q->state != UACCE_Q_STARTED)
+		return 0;
+
+	if (uacce->ops->stop_queue)
+		uacce->ops->stop_queue(q);
+
+	q->state = UACCE_Q_INIT;
+
+	return 0;
+}
+
+static void uacce_put_queue(struct uacce_queue *q)
+{
+	struct uacce_device *uacce = q->uacce;
+
+	uacce_stop_queue(q);
+
+	if (q->state != UACCE_Q_INIT)
+		return;
+
+	if (uacce->ops->put_queue)
+		uacce->ops->put_queue(q);
+
+	q->state = UACCE_Q_ZOMBIE;
+}
+
+static long uacce_fops_unl_ioctl(struct file *filep,
+				 unsigned int cmd, unsigned long arg)
+{
+	struct uacce_queue *q = filep->private_data;
+	struct uacce_device *uacce = q->uacce;
+	long ret = -ENXIO;
+
+	/*
+	 * uacce->ops->ioctl() may take the mmap_lock when copying arg to/from
+	 * user. Avoid a circular lock dependency with uacce_fops_mmap(), which
+	 * gets called with mmap_lock held, by taking uacce->mutex instead of
+	 * q->mutex. Doing this in uacce_fops_mmap() is not possible because
+	 * uacce_fops_open() calls iommu_sva_bind_device(), which takes
+	 * mmap_lock, while holding uacce->mutex.
+	 */
+	mutex_lock(&uacce->mutex);
+	if (!uacce_queue_is_valid(q))
+		goto out_unlock;
+
+	switch (cmd) {
+	case UACCE_CMD_START_Q:
+		ret = uacce_start_queue(q);
+		break;
+	case UACCE_CMD_PUT_Q:
+		ret = uacce_stop_queue(q);
+		break;
+	default:
+		if (uacce->ops->ioctl)
+			ret = uacce->ops->ioctl(q, cmd, arg);
+		else
+			ret = -EINVAL;
+	}
+out_unlock:
+	mutex_unlock(&uacce->mutex);
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static long uacce_fops_compat_ioctl(struct file *filep,
+				   unsigned int cmd, unsigned long arg)
+{
+	arg = (unsigned long)compat_ptr(arg);
+
+	return uacce_fops_unl_ioctl(filep, cmd, arg);
+}
+#endif
+
+static int uacce_bind_queue(struct uacce_device *uacce, struct uacce_queue *q)
+{
+	u32 pasid;
+	struct iommu_sva *handle;
+
+	if (!(uacce->flags & UACCE_DEV_SVA))
+		return 0;
+
+	handle = iommu_sva_bind_device(uacce->parent, current->mm);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	pasid = iommu_sva_get_pasid(handle);
+	if (pasid == IOMMU_PASID_INVALID) {
+		iommu_sva_unbind_device(handle);
+		return -ENODEV;
+	}
+
+	q->handle = handle;
+	q->pasid = pasid;
+	return 0;
+}
+
+static void uacce_unbind_queue(struct uacce_queue *q)
+{
+	if (!q->handle)
+		return;
+	iommu_sva_unbind_device(q->handle);
+	q->handle = NULL;
+}
+
+static int uacce_fops_open(struct inode *inode, struct file *filep)
+{
+	struct uacce_device *uacce;
+	struct uacce_queue *q;
+	int ret;
+
+	uacce = xa_load(&uacce_xa, iminor(inode));
+	if (!uacce)
+		return -ENODEV;
+
+	q = kzalloc_obj(struct uacce_queue);
+	if (!q)
+		return -ENOMEM;
+
+	mutex_lock(&uacce->mutex);
+
+	if (!uacce->parent) {
+		ret = -EINVAL;
+		goto out_with_mem;
+	}
+
+	ret = uacce_bind_queue(uacce, q);
+	if (ret)
+		goto out_with_mem;
+
+	q->uacce = uacce;
+
+	if (uacce->ops->get_queue) {
+		ret = uacce->ops->get_queue(uacce, q->pasid, q);
+		if (ret < 0)
+			goto out_with_bond;
+	}
+
+	init_waitqueue_head(&q->wait);
+	filep->private_data = q;
+	q->state = UACCE_Q_INIT;
+	q->mapping = filep->f_mapping;
+	mutex_init(&q->mutex);
+	list_add(&q->list, &uacce->queues);
+	mutex_unlock(&uacce->mutex);
+
+	return 0;
+
+out_with_bond:
+	uacce_unbind_queue(q);
+out_with_mem:
+	kfree(q);
+	mutex_unlock(&uacce->mutex);
+	return ret;
+}
+
+static int uacce_fops_release(struct inode *inode, struct file *filep)
+{
+	struct uacce_queue *q = filep->private_data;
+	struct uacce_device *uacce = q->uacce;
+
+	mutex_lock(&uacce->mutex);
+	uacce_put_queue(q);
+	uacce_unbind_queue(q);
+	list_del(&q->list);
+	mutex_unlock(&uacce->mutex);
+	kfree(q);
+
+	return 0;
+}
+
+static void uacce_vma_close(struct vm_area_struct *vma)
+{
+	struct uacce_queue *q = vma->vm_private_data;
+
+	if (vma->vm_pgoff < UACCE_MAX_REGION) {
+		struct uacce_qfile_region *qfr = q->qfrs[vma->vm_pgoff];
+
+		mutex_lock(&q->mutex);
+		q->qfrs[vma->vm_pgoff] = NULL;
+		mutex_unlock(&q->mutex);
+		kfree(qfr);
+	}
+}
+
+static int uacce_vma_mremap(struct vm_area_struct *area)
+{
+	return -EPERM;
+}
+
+static const struct vm_operations_struct uacce_vm_ops = {
+	.close = uacce_vma_close,
+	.mremap = uacce_vma_mremap,
+};
+
+static int uacce_fops_mmap(struct file *filep, struct vm_area_struct *vma)
+{
+	struct uacce_queue *q = filep->private_data;
+	struct uacce_device *uacce = q->uacce;
+	struct uacce_qfile_region *qfr;
+	enum uacce_qfrt type = UACCE_MAX_REGION;
+	int ret = 0;
+
+	if (vma->vm_pgoff < UACCE_MAX_REGION)
+		type = vma->vm_pgoff;
+	else
+		return -EINVAL;
+
+	qfr = kzalloc_obj(*qfr);
+	if (!qfr)
+		return -ENOMEM;
+
+	vm_flags_set(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_WIPEONFORK);
+	vma->vm_ops = &uacce_vm_ops;
+	vma->vm_private_data = q;
+	qfr->type = type;
+
+	mutex_lock(&q->mutex);
+	if (!uacce_queue_is_valid(q)) {
+		ret = -ENXIO;
+		goto out_with_lock;
+	}
+
+	if (q->qfrs[type]) {
+		ret = -EEXIST;
+		goto out_with_lock;
+	}
+
+	switch (type) {
+	case UACCE_QFRT_MMIO:
+	case UACCE_QFRT_DUS:
+		if (!uacce->ops->mmap) {
+			ret = -EINVAL;
+			goto out_with_lock;
+		}
+
+		ret = uacce->ops->mmap(q, vma, qfr);
+		if (ret)
+			goto out_with_lock;
+		break;
+
+	default:
+		ret = -EINVAL;
+		goto out_with_lock;
+	}
+
+	q->qfrs[type] = qfr;
+	mutex_unlock(&q->mutex);
+
+	return ret;
+
+out_with_lock:
+	mutex_unlock(&q->mutex);
+	kfree(qfr);
+	return ret;
+}
+
+static __poll_t uacce_fops_poll(struct file *file, poll_table *wait)
+{
+	struct uacce_queue *q = file->private_data;
+	struct uacce_device *uacce = q->uacce;
+	__poll_t ret = 0;
+
+	mutex_lock(&q->mutex);
+	if (!uacce_queue_is_valid(q))
+		goto out_unlock;
+
+	poll_wait(file, &q->wait, wait);
+
+	if (uacce->ops->is_q_updated && uacce->ops->is_q_updated(q))
+		ret = EPOLLIN | EPOLLRDNORM;
+
+out_unlock:
+	mutex_unlock(&q->mutex);
+	return ret;
+}
+
+static const struct file_operations uacce_fops = {
+	.owner		= THIS_MODULE,
+	.open		= uacce_fops_open,
+	.release	= uacce_fops_release,
+	.unlocked_ioctl	= uacce_fops_unl_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= uacce_fops_compat_ioctl,
+#endif
+	.mmap		= uacce_fops_mmap,
+	.poll		= uacce_fops_poll,
+};
+
+#define to_uacce_device(dev) container_of(dev, struct uacce_device, dev)
+
+static ssize_t api_show(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%s\n", uacce->api_ver);
+}
+
+static ssize_t flags_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%u\n", uacce->flags);
+}
+
+static ssize_t available_instances_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	if (!uacce->ops->get_available_instances)
+		return -ENODEV;
+
+	return sysfs_emit(buf, "%d\n",
+		       uacce->ops->get_available_instances(uacce));
+}
+
+static ssize_t algorithms_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%s\n", uacce->algs);
+}
+
+static ssize_t region_mmio_size_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%lu\n",
+		       uacce->qf_pg_num[UACCE_QFRT_MMIO] << PAGE_SHIFT);
+}
+
+static ssize_t region_dus_size_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%lu\n",
+		       uacce->qf_pg_num[UACCE_QFRT_DUS] << PAGE_SHIFT);
+}
+
+static ssize_t isolate_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	return sysfs_emit(buf, "%d\n", uacce->ops->get_isolate_state(uacce));
+}
+
+static ssize_t isolate_strategy_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+	u32 val;
+
+	if (!uacce->ops->isolate_err_threshold_read)
+		return -ENOENT;
+
+	val = uacce->ops->isolate_err_threshold_read(uacce);
+
+	return sysfs_emit(buf, "%u\n", val);
+}
+
+static ssize_t isolate_strategy_store(struct device *dev, struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+	unsigned long val;
+	int ret;
+
+	if (!uacce->ops->isolate_err_threshold_write)
+		return -ENOENT;
+
+	if (kstrtoul(buf, 0, &val) < 0)
+		return -EINVAL;
+
+	if (val > UACCE_MAX_ERR_THRESHOLD)
+		return -EINVAL;
+
+	ret = uacce->ops->isolate_err_threshold_write(uacce, val);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static DEVICE_ATTR_RO(api);
+static DEVICE_ATTR_RO(flags);
+static DEVICE_ATTR_RO(available_instances);
+static DEVICE_ATTR_RO(algorithms);
+static DEVICE_ATTR_RO(region_mmio_size);
+static DEVICE_ATTR_RO(region_dus_size);
+static DEVICE_ATTR_RO(isolate);
+static DEVICE_ATTR_RW(isolate_strategy);
+
+static struct attribute *uacce_dev_attrs[] = {
+	&dev_attr_api.attr,
+	&dev_attr_flags.attr,
+	&dev_attr_available_instances.attr,
+	&dev_attr_algorithms.attr,
+	&dev_attr_region_mmio_size.attr,
+	&dev_attr_region_dus_size.attr,
+	&dev_attr_isolate.attr,
+	&dev_attr_isolate_strategy.attr,
+	NULL,
+};
+
+static umode_t uacce_dev_is_visible(struct kobject *kobj,
+				    struct attribute *attr, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	if (((attr == &dev_attr_region_mmio_size.attr) &&
+	    (!uacce->qf_pg_num[UACCE_QFRT_MMIO])) ||
+	    ((attr == &dev_attr_region_dus_size.attr) &&
+	    (!uacce->qf_pg_num[UACCE_QFRT_DUS])))
+		return 0;
+
+	if (attr == &dev_attr_isolate_strategy.attr &&
+	    (!uacce->ops->isolate_err_threshold_read &&
+	     !uacce->ops->isolate_err_threshold_write))
+		return 0;
+
+	if (attr == &dev_attr_isolate.attr && !uacce->ops->get_isolate_state)
+		return 0;
+
+	return attr->mode;
+}
+
+static struct attribute_group uacce_dev_group = {
+	.is_visible	= uacce_dev_is_visible,
+	.attrs		= uacce_dev_attrs,
+};
+
+__ATTRIBUTE_GROUPS(uacce_dev);
+
+static void uacce_release(struct device *dev)
+{
+	struct uacce_device *uacce = to_uacce_device(dev);
+
+	kfree(uacce);
+}
+
+/**
+ * uacce_alloc() - alloc an accelerator
+ * @parent: pointer of uacce parent device
+ * @interface: pointer of uacce_interface for register
+ *
+ * Returns uacce pointer if success and ERR_PTR if not
+ * Need check returned negotiated uacce->flags
+ */
+struct uacce_device *uacce_alloc(struct device *parent,
+				 struct uacce_interface *interface)
+{
+	unsigned int flags = interface->flags;
+	struct uacce_device *uacce;
+	int ret;
+
+	uacce = kzalloc_obj(struct uacce_device);
+	if (!uacce)
+		return ERR_PTR(-ENOMEM);
+
+	uacce->parent = parent;
+	uacce->flags = flags;
+	uacce->ops = interface->ops;
+
+	ret = xa_alloc(&uacce_xa, &uacce->dev_id, uacce, xa_limit_32b,
+		       GFP_KERNEL);
+	if (ret < 0)
+		goto err_with_uacce;
+
+	INIT_LIST_HEAD(&uacce->queues);
+	mutex_init(&uacce->mutex);
+	device_initialize(&uacce->dev);
+	uacce->dev.devt = MKDEV(MAJOR(uacce_devt), uacce->dev_id);
+	uacce->dev.class = &uacce_class;
+	uacce->dev.groups = uacce_dev_groups;
+	uacce->dev.parent = uacce->parent;
+	uacce->dev.release = uacce_release;
+	dev_set_name(&uacce->dev, "%s-%d", interface->name, uacce->dev_id);
+
+	return uacce;
+
+err_with_uacce:
+	kfree(uacce);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(uacce_alloc);
+
+/**
+ * uacce_register() - add the accelerator to cdev and export to user space
+ * @uacce: The initialized uacce device
+ *
+ * Return 0 if register succeeded, or an error.
+ */
+int uacce_register(struct uacce_device *uacce)
+{
+	int ret;
+
+	if (!uacce)
+		return -ENODEV;
+
+	uacce->cdev = cdev_alloc();
+	if (!uacce->cdev)
+		return -ENOMEM;
+
+	uacce->cdev->ops = &uacce_fops;
+	uacce->cdev->owner = THIS_MODULE;
+
+	ret = cdev_device_add(uacce->cdev, &uacce->dev);
+	if (ret)
+		uacce->cdev = NULL;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(uacce_register);
+
+/**
+ * uacce_remove() - remove the accelerator
+ * @uacce: the accelerator to remove
+ */
+void uacce_remove(struct uacce_device *uacce)
+{
+	struct uacce_queue *q, *next_q;
+
+	if (!uacce)
+		return;
+
+	/*
+	 * uacce_fops_open() may be running concurrently, even after we remove
+	 * the cdev. Holding uacce->mutex ensures that open() does not obtain a
+	 * removed uacce device.
+	 */
+	mutex_lock(&uacce->mutex);
+	/* ensure no open queue remains */
+	list_for_each_entry_safe(q, next_q, &uacce->queues, list) {
+		/*
+		 * Taking q->mutex ensures that fops do not use the defunct
+		 * uacce->ops after the queue is disabled.
+		 */
+		mutex_lock(&q->mutex);
+		uacce_put_queue(q);
+		mutex_unlock(&q->mutex);
+		uacce_unbind_queue(q);
+
+		/*
+		 * unmap remaining mapping from user space, preventing user still
+		 * access the mmaped area while parent device is already removed
+		 */
+		unmap_mapping_range(q->mapping, 0, 0, 1);
+	}
+
+	if (uacce->cdev)
+		cdev_device_del(uacce->cdev, &uacce->dev);
+	xa_erase(&uacce_xa, uacce->dev_id);
+	/*
+	 * uacce exists as long as there are open fds, but ops will be freed
+	 * now. Ensure that bugs cause NULL deref rather than use-after-free.
+	 */
+	uacce->ops = NULL;
+	uacce->parent = NULL;
+	mutex_unlock(&uacce->mutex);
+	put_device(&uacce->dev);
+}
+EXPORT_SYMBOL_GPL(uacce_remove);
+
+static int __init uacce_init(void)
+{
+	int ret;
+
+	ret = class_register(&uacce_class);
+	if (ret)
+		return ret;
+
+	ret = alloc_chrdev_region(&uacce_devt, 0, MINORMASK, UACCE_NAME);
+	if (ret)
+		class_unregister(&uacce_class);
+
+	return ret;
+}
+
+static __exit void uacce_exit(void)
+{
+	unregister_chrdev_region(uacce_devt, MINORMASK);
+	class_unregister(&uacce_class);
+}
+
+subsys_initcall(uacce_init);
+module_exit(uacce_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("HiSilicon Tech. Co., Ltd.");
+MODULE_DESCRIPTION("Accelerator interface for Userland applications");