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, 258 insertions, 0 deletions

diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
new file mode 100644
index 000000000..9aa306621
--- /dev/null
+++ b/drivers/phy/phy-can-transceiver.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * phy-can-transceiver.c - phy driver for CAN transceivers
+ *
+ * Copyright (C) 2021 Texas Instruments Incorporated - https://www.ti.com
+ *
+ */
+#include <linux/gpio/consumer.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/module.h>
+#include <linux/mux/consumer.h>
+
+struct can_transceiver_data {
+	u32 flags;
+#define CAN_TRANSCEIVER_STB_PRESENT	BIT(0)
+#define CAN_TRANSCEIVER_EN_PRESENT	BIT(1)
+#define CAN_TRANSCEIVER_DUAL_CH		BIT(2)
+#define CAN_TRANSCEIVER_SILENT_PRESENT	BIT(3)
+};
+
+struct can_transceiver_phy {
+	struct phy *generic_phy;
+	struct gpio_desc *silent_gpio;
+	struct gpio_desc *standby_gpio;
+	struct gpio_desc *enable_gpio;
+	struct can_transceiver_priv *priv;
+};
+
+struct can_transceiver_priv {
+	struct mux_state *mux_state;
+	int num_ch;
+	struct can_transceiver_phy can_transceiver_phy[] __counted_by(num_ch);
+};
+
+/* Power on function */
+static int can_transceiver_phy_power_on(struct phy *phy)
+{
+	struct can_transceiver_phy *can_transceiver_phy = phy_get_drvdata(phy);
+	struct can_transceiver_priv *priv = can_transceiver_phy->priv;
+	int ret;
+
+	if (priv->mux_state) {
+		ret = mux_state_select(priv->mux_state);
+		if (ret) {
+			dev_err(&phy->dev, "Failed to select CAN mux: %d\n", ret);
+			return ret;
+		}
+	}
+	gpiod_set_value_cansleep(can_transceiver_phy->silent_gpio, 0);
+	gpiod_set_value_cansleep(can_transceiver_phy->standby_gpio, 0);
+	gpiod_set_value_cansleep(can_transceiver_phy->enable_gpio, 1);
+
+	return 0;
+}
+
+/* Power off function */
+static int can_transceiver_phy_power_off(struct phy *phy)
+{
+	struct can_transceiver_phy *can_transceiver_phy = phy_get_drvdata(phy);
+	struct can_transceiver_priv *priv = can_transceiver_phy->priv;
+
+	gpiod_set_value_cansleep(can_transceiver_phy->silent_gpio, 1);
+	gpiod_set_value_cansleep(can_transceiver_phy->standby_gpio, 1);
+	gpiod_set_value_cansleep(can_transceiver_phy->enable_gpio, 0);
+	if (priv->mux_state)
+		mux_state_deselect(priv->mux_state);
+
+	return 0;
+}
+
+static const struct phy_ops can_transceiver_phy_ops = {
+	.power_on	= can_transceiver_phy_power_on,
+	.power_off	= can_transceiver_phy_power_off,
+	.owner		= THIS_MODULE,
+};
+
+static const struct can_transceiver_data tcan1042_drvdata = {
+	.flags = CAN_TRANSCEIVER_STB_PRESENT,
+};
+
+static const struct can_transceiver_data tcan1043_drvdata = {
+	.flags = CAN_TRANSCEIVER_STB_PRESENT | CAN_TRANSCEIVER_EN_PRESENT,
+};
+
+static const struct can_transceiver_data tja1048_drvdata = {
+	.flags = CAN_TRANSCEIVER_STB_PRESENT | CAN_TRANSCEIVER_DUAL_CH,
+};
+
+static const struct can_transceiver_data tja1051_drvdata = {
+	.flags = CAN_TRANSCEIVER_SILENT_PRESENT | CAN_TRANSCEIVER_EN_PRESENT,
+};
+
+static const struct can_transceiver_data tja1057_drvdata = {
+	.flags = CAN_TRANSCEIVER_SILENT_PRESENT,
+};
+
+static struct phy *can_transceiver_phy_xlate(struct device *dev,
+					     const struct of_phandle_args *args)
+{
+	struct can_transceiver_priv *priv = dev_get_drvdata(dev);
+	u32 idx;
+
+	if (priv->num_ch == 1)
+		return priv->can_transceiver_phy[0].generic_phy;
+
+	if (args->args_count != 1)
+		return ERR_PTR(-EINVAL);
+
+	idx = args->args[0];
+	if (idx >= priv->num_ch)
+		return ERR_PTR(-EINVAL);
+
+	return priv->can_transceiver_phy[idx].generic_phy;
+}
+
+static int can_transceiver_phy_probe(struct platform_device *pdev)
+{
+	struct phy_provider *phy_provider;
+	struct device *dev = &pdev->dev;
+	struct can_transceiver_phy *can_transceiver_phy;
+	struct can_transceiver_priv *priv;
+	const struct can_transceiver_data *drvdata;
+	struct phy *phy;
+	struct gpio_desc *silent_gpio;
+	struct gpio_desc *standby_gpio;
+	struct gpio_desc *enable_gpio;
+	struct mux_state *mux_state;
+	const char *propname;
+	int err, i, num_ch;
+	u32 max_bitrate;
+
+	drvdata = device_get_match_data(dev);
+	if (!drvdata)
+		return -ENODEV;
+
+	if (drvdata->flags & CAN_TRANSCEIVER_DUAL_CH)
+		num_ch = 2;
+	else
+		num_ch = 1;
+
+	priv = devm_kzalloc(dev, struct_size(priv, can_transceiver_phy, num_ch), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->num_ch = num_ch;
+	platform_set_drvdata(pdev, priv);
+
+	mux_state = devm_mux_state_get_optional(dev, NULL);
+	if (IS_ERR(mux_state))
+		return PTR_ERR(mux_state);
+
+	priv->mux_state = mux_state;
+
+	propname = "max-bitrate";
+	if (device_property_present(dev, propname)) {
+		err = device_property_read_u32(dev, propname, &max_bitrate);
+		if (err)
+			return dev_err_probe(dev, err, "failed to parse %s\n", propname);
+
+		if (max_bitrate == 0)
+			dev_warn(dev, "Invalid value for transceiver max bitrate. Ignoring bitrate limit\n");
+	} else {
+		max_bitrate = 0;
+	}
+
+	for (i = 0; i < num_ch; i++) {
+		can_transceiver_phy = &priv->can_transceiver_phy[i];
+		can_transceiver_phy->priv = priv;
+
+		phy = devm_phy_create(dev, NULL, &can_transceiver_phy_ops);
+		if (IS_ERR(phy)) {
+			dev_err(dev, "failed to create can transceiver phy\n");
+			return PTR_ERR(phy);
+		}
+
+		phy->attrs.max_link_rate = max_bitrate;
+
+		can_transceiver_phy->generic_phy = phy;
+		can_transceiver_phy->priv = priv;
+
+		if (drvdata->flags & CAN_TRANSCEIVER_STB_PRESENT) {
+			standby_gpio = devm_gpiod_get_index_optional(dev, "standby", i,
+								     GPIOD_OUT_HIGH);
+			if (IS_ERR(standby_gpio))
+				return PTR_ERR(standby_gpio);
+			can_transceiver_phy->standby_gpio = standby_gpio;
+		}
+
+		if (drvdata->flags & CAN_TRANSCEIVER_EN_PRESENT) {
+			enable_gpio = devm_gpiod_get_index_optional(dev, "enable", i,
+								    GPIOD_OUT_LOW);
+			if (IS_ERR(enable_gpio))
+				return PTR_ERR(enable_gpio);
+			can_transceiver_phy->enable_gpio = enable_gpio;
+		}
+
+		if (drvdata->flags & CAN_TRANSCEIVER_SILENT_PRESENT) {
+			silent_gpio = devm_gpiod_get_index_optional(dev, "silent", i,
+								    GPIOD_OUT_HIGH);
+			if (IS_ERR(silent_gpio))
+				return PTR_ERR(silent_gpio);
+			can_transceiver_phy->silent_gpio = silent_gpio;
+		}
+
+		phy_set_drvdata(can_transceiver_phy->generic_phy, can_transceiver_phy);
+
+	}
+
+	phy_provider = devm_of_phy_provider_register(dev, can_transceiver_phy_xlate);
+
+	return PTR_ERR_OR_ZERO(phy_provider);
+}
+
+static const struct of_device_id can_transceiver_phy_ids[] = {
+	{
+		.compatible = "ti,tcan1042",
+		.data = &tcan1042_drvdata
+	},
+	{
+		.compatible = "ti,tcan1043",
+		.data = &tcan1043_drvdata
+	},
+	{
+		.compatible = "nxp,tja1048",
+		.data = &tja1048_drvdata
+	},
+	{
+		.compatible = "nxp,tja1051",
+		.data = &tja1051_drvdata
+	},
+	{
+		.compatible = "nxp,tja1057",
+		.data = &tja1057_drvdata
+	},
+	{
+		.compatible = "nxp,tjr1443",
+		.data = &tcan1043_drvdata
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, can_transceiver_phy_ids);
+
+static struct platform_driver can_transceiver_phy_driver = {
+	.probe = can_transceiver_phy_probe,
+	.driver = {
+		.name = "can-transceiver-phy",
+		.of_match_table = can_transceiver_phy_ids,
+	},
+};
+
+module_platform_driver(can_transceiver_phy_driver);
+
+MODULE_AUTHOR("Faiz Abbas <faiz_abbas@ti.com>");
+MODULE_AUTHOR("Aswath Govindraju <a-govindraju@ti.com>");
+MODULE_DESCRIPTION("CAN TRANSCEIVER PHY driver");
+MODULE_LICENSE("GPL v2");