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, 426 insertions, 0 deletions

diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
new file mode 100644
index 000000000..e3bd0b961
--- /dev/null
+++ b/drivers/virtio/virtio_input.c
@@ -0,0 +1,426 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/dma-mapping.h>
+
+#include <uapi/linux/virtio_ids.h>
+#include <uapi/linux/virtio_input.h>
+#include <linux/input/mt.h>
+
+struct virtio_input {
+	struct virtio_device       *vdev;
+	struct input_dev           *idev;
+	char                       name[64];
+	char                       serial[64];
+	char                       phys[64];
+	struct virtqueue           *evt, *sts;
+	__dma_from_device_group_begin();
+	struct virtio_input_event  evts[64];
+	__dma_from_device_group_end();
+	spinlock_t                 lock;
+	bool                       ready;
+};
+
+static void virtinput_queue_evtbuf(struct virtio_input *vi,
+				   struct virtio_input_event *evtbuf)
+{
+	struct scatterlist sg[1];
+
+	sg_init_one(sg, evtbuf, sizeof(*evtbuf));
+	virtqueue_add_inbuf_cache_clean(vi->evt, sg, 1, evtbuf, GFP_ATOMIC);
+}
+
+static void virtinput_recv_events(struct virtqueue *vq)
+{
+	struct virtio_input *vi = vq->vdev->priv;
+	struct virtio_input_event *event;
+	unsigned long flags;
+	unsigned int len;
+
+	spin_lock_irqsave(&vi->lock, flags);
+	if (vi->ready) {
+		while ((event = virtqueue_get_buf(vi->evt, &len)) != NULL) {
+			spin_unlock_irqrestore(&vi->lock, flags);
+			input_event(vi->idev,
+				    le16_to_cpu(event->type),
+				    le16_to_cpu(event->code),
+				    le32_to_cpu(event->value));
+			spin_lock_irqsave(&vi->lock, flags);
+			if (!vi->ready)
+				continue;
+			virtinput_queue_evtbuf(vi, event);
+		}
+		if (vi->ready)
+			virtqueue_kick(vq);
+	}
+	spin_unlock_irqrestore(&vi->lock, flags);
+}
+
+/*
+ * On error we are losing the status update, which isn't critical as
+ * this is typically used for stuff like keyboard leds.
+ */
+static int virtinput_send_status(struct virtio_input *vi,
+				 u16 type, u16 code, s32 value)
+{
+	struct virtio_input_event *stsbuf;
+	struct scatterlist sg[1];
+	unsigned long flags;
+	int rc;
+
+	/*
+	 * Since 29cc309d8bf1 (HID: hid-multitouch: forward MSC_TIMESTAMP),
+	 * EV_MSC/MSC_TIMESTAMP is added to each before EV_SYN event.
+	 * EV_MSC is configured as INPUT_PASS_TO_ALL.
+	 * In case of touch device:
+	 *   BE pass EV_MSC/MSC_TIMESTAMP to FE on receiving event from evdev.
+	 *   FE pass EV_MSC/MSC_TIMESTAMP back to BE.
+	 *   BE writes EV_MSC/MSC_TIMESTAMP to evdev due to INPUT_PASS_TO_ALL.
+	 *   BE receives extra EV_MSC/MSC_TIMESTAMP and pass to FE.
+	 *   >>> Each new frame becomes larger and larger.
+	 * Disable EV_MSC/MSC_TIMESTAMP forwarding for MT.
+	 */
+	if (vi->idev->mt && type == EV_MSC && code == MSC_TIMESTAMP)
+		return 0;
+
+	stsbuf = kzalloc_obj(*stsbuf, GFP_ATOMIC);
+	if (!stsbuf)
+		return -ENOMEM;
+
+	stsbuf->type  = cpu_to_le16(type);
+	stsbuf->code  = cpu_to_le16(code);
+	stsbuf->value = cpu_to_le32(value);
+	sg_init_one(sg, stsbuf, sizeof(*stsbuf));
+
+	spin_lock_irqsave(&vi->lock, flags);
+	if (vi->ready) {
+		rc = virtqueue_add_outbuf(vi->sts, sg, 1, stsbuf, GFP_ATOMIC);
+		virtqueue_kick(vi->sts);
+	} else {
+		rc = -ENODEV;
+	}
+	spin_unlock_irqrestore(&vi->lock, flags);
+
+	if (rc != 0)
+		kfree(stsbuf);
+	return rc;
+}
+
+static void virtinput_recv_status(struct virtqueue *vq)
+{
+	struct virtio_input *vi = vq->vdev->priv;
+	struct virtio_input_event *stsbuf;
+	unsigned long flags;
+	unsigned int len;
+
+	spin_lock_irqsave(&vi->lock, flags);
+	while ((stsbuf = virtqueue_get_buf(vi->sts, &len)) != NULL)
+		kfree(stsbuf);
+	spin_unlock_irqrestore(&vi->lock, flags);
+}
+
+static int virtinput_status(struct input_dev *idev, unsigned int type,
+			    unsigned int code, int value)
+{
+	struct virtio_input *vi = input_get_drvdata(idev);
+
+	return virtinput_send_status(vi, type, code, value);
+}
+
+static u8 virtinput_cfg_select(struct virtio_input *vi,
+			       u8 select, u8 subsel)
+{
+	u8 size;
+
+	virtio_cwrite_le(vi->vdev, struct virtio_input_config, select, &select);
+	virtio_cwrite_le(vi->vdev, struct virtio_input_config, subsel, &subsel);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, size, &size);
+	return size;
+}
+
+static void virtinput_cfg_bits(struct virtio_input *vi, int select, int subsel,
+			       unsigned long *bits, unsigned int bitcount)
+{
+	unsigned int bit;
+	u8 *virtio_bits;
+	u8 bytes;
+
+	bytes = virtinput_cfg_select(vi, select, subsel);
+	if (!bytes)
+		return;
+	if (bitcount > bytes * 8)
+		bitcount = bytes * 8;
+
+	/*
+	 * Bitmap in virtio config space is a simple stream of bytes,
+	 * with the first byte carrying bits 0-7, second bits 8-15 and
+	 * so on.
+	 */
+	virtio_bits = kzalloc(bytes, GFP_KERNEL);
+	if (!virtio_bits)
+		return;
+	virtio_cread_bytes(vi->vdev, offsetof(struct virtio_input_config,
+					      u.bitmap),
+			   virtio_bits, bytes);
+	for (bit = 0; bit < bitcount; bit++) {
+		if (virtio_bits[bit / 8] & (1 << (bit % 8)))
+			__set_bit(bit, bits);
+	}
+	kfree(virtio_bits);
+
+	if (select == VIRTIO_INPUT_CFG_EV_BITS)
+		__set_bit(subsel, vi->idev->evbit);
+}
+
+static void virtinput_cfg_abs(struct virtio_input *vi, int abs)
+{
+	u32 mi, ma, re, fu, fl;
+
+	virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ABS_INFO, abs);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, u.abs.min, &mi);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, u.abs.max, &ma);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, u.abs.res, &re);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, u.abs.fuzz, &fu);
+	virtio_cread_le(vi->vdev, struct virtio_input_config, u.abs.flat, &fl);
+	input_set_abs_params(vi->idev, abs, mi, ma, fu, fl);
+	input_abs_set_res(vi->idev, abs, re);
+}
+
+static int virtinput_init_vqs(struct virtio_input *vi)
+{
+	struct virtqueue_info vqs_info[] = {
+		{ "events", virtinput_recv_events },
+		{ "status", virtinput_recv_status },
+	};
+	struct virtqueue *vqs[2];
+	int err;
+
+	err = virtio_find_vqs(vi->vdev, 2, vqs, vqs_info, NULL);
+	if (err)
+		return err;
+	vi->evt = vqs[0];
+	vi->sts = vqs[1];
+
+	return 0;
+}
+
+static void virtinput_fill_evt(struct virtio_input *vi)
+{
+	unsigned long flags;
+	int i, size;
+
+	spin_lock_irqsave(&vi->lock, flags);
+	size = virtqueue_get_vring_size(vi->evt);
+	if (size > ARRAY_SIZE(vi->evts))
+		size = ARRAY_SIZE(vi->evts);
+	for (i = 0; i < size; i++)
+		virtinput_queue_evtbuf(vi, &vi->evts[i]);
+	virtqueue_kick(vi->evt);
+	spin_unlock_irqrestore(&vi->lock, flags);
+}
+
+static int virtinput_probe(struct virtio_device *vdev)
+{
+	struct virtio_input *vi;
+	unsigned long flags;
+	size_t size;
+	int abs, err, nslots;
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1))
+		return -ENODEV;
+
+	vi = kzalloc_obj(*vi);
+	if (!vi)
+		return -ENOMEM;
+
+	vdev->priv = vi;
+	vi->vdev = vdev;
+	spin_lock_init(&vi->lock);
+
+	err = virtinput_init_vqs(vi);
+	if (err)
+		goto err_init_vq;
+
+	vi->idev = input_allocate_device();
+	if (!vi->idev) {
+		err = -ENOMEM;
+		goto err_input_alloc;
+	}
+	input_set_drvdata(vi->idev, vi);
+
+	size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ID_NAME, 0);
+	virtio_cread_bytes(vi->vdev, offsetof(struct virtio_input_config,
+					      u.string),
+			   vi->name, min(size, sizeof(vi->name)));
+	size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ID_SERIAL, 0);
+	virtio_cread_bytes(vi->vdev, offsetof(struct virtio_input_config,
+					      u.string),
+			   vi->serial, min(size, sizeof(vi->serial)));
+	snprintf(vi->phys, sizeof(vi->phys),
+		 "virtio%d/input0", vdev->index);
+	vi->idev->name = vi->name;
+	vi->idev->phys = vi->phys;
+	vi->idev->uniq = vi->serial;
+
+	size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_ID_DEVIDS, 0);
+	if (size >= sizeof(struct virtio_input_devids)) {
+		virtio_cread_le(vi->vdev, struct virtio_input_config,
+				u.ids.bustype, &vi->idev->id.bustype);
+		virtio_cread_le(vi->vdev, struct virtio_input_config,
+				u.ids.vendor, &vi->idev->id.vendor);
+		virtio_cread_le(vi->vdev, struct virtio_input_config,
+				u.ids.product, &vi->idev->id.product);
+		virtio_cread_le(vi->vdev, struct virtio_input_config,
+				u.ids.version, &vi->idev->id.version);
+	} else {
+		vi->idev->id.bustype = BUS_VIRTUAL;
+	}
+
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_PROP_BITS, 0,
+			   vi->idev->propbit, INPUT_PROP_CNT);
+	size = virtinput_cfg_select(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_REP);
+	if (size)
+		__set_bit(EV_REP, vi->idev->evbit);
+
+	vi->idev->dev.parent = &vdev->dev;
+	vi->idev->event = virtinput_status;
+
+	/* device -> kernel */
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_KEY,
+			   vi->idev->keybit, KEY_CNT);
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_REL,
+			   vi->idev->relbit, REL_CNT);
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_ABS,
+			   vi->idev->absbit, ABS_CNT);
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_MSC,
+			   vi->idev->mscbit, MSC_CNT);
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_SW,
+			   vi->idev->swbit,  SW_CNT);
+
+	/* kernel -> device */
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_LED,
+			   vi->idev->ledbit, LED_CNT);
+	virtinput_cfg_bits(vi, VIRTIO_INPUT_CFG_EV_BITS, EV_SND,
+			   vi->idev->sndbit, SND_CNT);
+
+	if (test_bit(EV_ABS, vi->idev->evbit)) {
+		for (abs = 0; abs < ABS_CNT; abs++) {
+			if (!test_bit(abs, vi->idev->absbit))
+				continue;
+			virtinput_cfg_abs(vi, abs);
+		}
+
+		if (test_bit(ABS_MT_SLOT, vi->idev->absbit)) {
+			nslots = input_abs_get_max(vi->idev, ABS_MT_SLOT) + 1;
+			err = input_mt_init_slots(vi->idev, nslots, 0);
+			if (err)
+				goto err_mt_init_slots;
+		}
+	}
+
+	virtio_device_ready(vdev);
+	vi->ready = true;
+	err = input_register_device(vi->idev);
+	if (err)
+		goto err_input_register;
+
+	virtinput_fill_evt(vi);
+	return 0;
+
+err_input_register:
+	spin_lock_irqsave(&vi->lock, flags);
+	vi->ready = false;
+	spin_unlock_irqrestore(&vi->lock, flags);
+	virtio_reset_device(vdev);
+err_mt_init_slots:
+	input_free_device(vi->idev);
+err_input_alloc:
+	vdev->config->del_vqs(vdev);
+err_init_vq:
+	kfree(vi);
+	return err;
+}
+
+static void virtinput_remove(struct virtio_device *vdev)
+{
+	struct virtio_input *vi = vdev->priv;
+	void *buf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&vi->lock, flags);
+	vi->ready = false;
+	spin_unlock_irqrestore(&vi->lock, flags);
+
+	/* Callbacks use vi->idev. */
+	virtio_reset_device(vdev);
+	input_unregister_device(vi->idev);
+	while ((buf = virtqueue_detach_unused_buf(vi->sts)) != NULL)
+		kfree(buf);
+	vdev->config->del_vqs(vdev);
+	kfree(vi);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtinput_freeze(struct virtio_device *vdev)
+{
+	struct virtio_input *vi = vdev->priv;
+	unsigned long flags;
+	void *buf;
+
+	spin_lock_irqsave(&vi->lock, flags);
+	vi->ready = false;
+	spin_unlock_irqrestore(&vi->lock, flags);
+
+	virtio_reset_device(vdev);
+	while ((buf = virtqueue_detach_unused_buf(vi->sts)) != NULL)
+		kfree(buf);
+	vdev->config->del_vqs(vdev);
+	return 0;
+}
+
+static int virtinput_restore(struct virtio_device *vdev)
+{
+	struct virtio_input *vi = vdev->priv;
+	int err;
+
+	err = virtinput_init_vqs(vi);
+	if (err)
+		return err;
+
+	virtio_device_ready(vdev);
+	vi->ready = true;
+	virtinput_fill_evt(vi);
+	return 0;
+}
+#endif
+
+static unsigned int features[] = {
+	/* none */
+};
+static const struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_INPUT, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_input_driver = {
+	.driver.name         = KBUILD_MODNAME,
+	.feature_table       = features,
+	.feature_table_size  = ARRAY_SIZE(features),
+	.id_table            = id_table,
+	.probe               = virtinput_probe,
+	.remove              = virtinput_remove,
+#ifdef CONFIG_PM_SLEEP
+	.freeze	             = virtinput_freeze,
+	.restore             = virtinput_restore,
+#endif
+};
+
+module_virtio_driver(virtio_input_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtio input device driver");
+MODULE_AUTHOR("Gerd Hoffmann <kraxel@redhat.com>");