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, 221 insertions, 0 deletions

diff --git a/drivers/input/serio/ioc3kbd.c b/drivers/input/serio/ioc3kbd.c
new file mode 100644
index 000000000..4ef60c24e
--- /dev/null
+++ b/drivers/input/serio/ioc3kbd.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SGI IOC3 PS/2 controller driver for linux
+ *
+ * Copyright (C) 2019 Thomas Bogendoerfer <tbogendoerfer@suse.de>
+ *
+ * Based on code Copyright (C) 2005 Stanislaw Skowronek <skylark@unaligned.org>
+ *               Copyright (C) 2009 Johannes Dickgreber <tanzy@gmx.de>
+ */
+
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/serio.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <asm/sn/ioc3.h>
+
+struct ioc3kbd_data {
+	struct ioc3_serioregs __iomem *regs;
+	struct serio *kbd, *aux;
+	bool kbd_exists, aux_exists;
+	int irq;
+};
+
+static int ioc3kbd_wait(struct ioc3_serioregs __iomem *regs, u32 mask)
+{
+	unsigned long timeout = 0;
+
+	while ((readl(&regs->km_csr) & mask) && (timeout < 250)) {
+		udelay(50);
+		timeout++;
+	}
+	return (timeout >= 250) ? -ETIMEDOUT : 0;
+}
+
+static int ioc3kbd_write(struct serio *dev, u8 val)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+	int ret;
+
+	ret = ioc3kbd_wait(d->regs, KM_CSR_K_WRT_PEND);
+	if (ret)
+		return ret;
+
+	writel(val, &d->regs->k_wd);
+
+	return 0;
+}
+
+static int ioc3kbd_start(struct serio *dev)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+
+	d->kbd_exists = true;
+	return 0;
+}
+
+static void ioc3kbd_stop(struct serio *dev)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+
+	d->kbd_exists = false;
+}
+
+static int ioc3aux_write(struct serio *dev, u8 val)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+	int ret;
+
+	ret = ioc3kbd_wait(d->regs, KM_CSR_M_WRT_PEND);
+	if (ret)
+		return ret;
+
+	writel(val, &d->regs->m_wd);
+
+	return 0;
+}
+
+static int ioc3aux_start(struct serio *dev)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+
+	d->aux_exists = true;
+	return 0;
+}
+
+static void ioc3aux_stop(struct serio *dev)
+{
+	struct ioc3kbd_data *d = dev->port_data;
+
+	d->aux_exists = false;
+}
+
+static void ioc3kbd_process_data(struct serio *dev, u32 data)
+{
+	if (data & KM_RD_VALID_0)
+		serio_interrupt(dev, (data >> KM_RD_DATA_0_SHIFT) & 0xff, 0);
+	if (data & KM_RD_VALID_1)
+		serio_interrupt(dev, (data >> KM_RD_DATA_1_SHIFT) & 0xff, 0);
+	if (data & KM_RD_VALID_2)
+		serio_interrupt(dev, (data >> KM_RD_DATA_2_SHIFT) & 0xff, 0);
+}
+
+static irqreturn_t ioc3kbd_intr(int itq, void *dev_id)
+{
+	struct ioc3kbd_data *d = dev_id;
+	u32 data_k, data_m;
+
+	data_k = readl(&d->regs->k_rd);
+	if (d->kbd_exists)
+		ioc3kbd_process_data(d->kbd, data_k);
+
+	data_m = readl(&d->regs->m_rd);
+	if (d->aux_exists)
+		ioc3kbd_process_data(d->aux, data_m);
+
+	return IRQ_HANDLED;
+}
+
+static int ioc3kbd_probe(struct platform_device *pdev)
+{
+	struct ioc3_serioregs __iomem *regs;
+	struct device *dev = &pdev->dev;
+	struct ioc3kbd_data *d;
+	struct serio *sk, *sa;
+	int irq, ret;
+
+	regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return -ENXIO;
+
+	d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
+	if (!d)
+		return -ENOMEM;
+
+	sk = kzalloc_obj(*sk);
+	if (!sk)
+		return -ENOMEM;
+
+	sa = kzalloc_obj(*sa);
+	if (!sa) {
+		kfree(sk);
+		return -ENOMEM;
+	}
+
+	sk->id.type = SERIO_8042;
+	sk->write = ioc3kbd_write;
+	sk->start = ioc3kbd_start;
+	sk->stop = ioc3kbd_stop;
+	snprintf(sk->name, sizeof(sk->name), "IOC3 keyboard %d", pdev->id);
+	snprintf(sk->phys, sizeof(sk->phys), "ioc3/serio%dkbd", pdev->id);
+	sk->port_data = d;
+	sk->dev.parent = dev;
+
+	sa->id.type = SERIO_8042;
+	sa->write = ioc3aux_write;
+	sa->start = ioc3aux_start;
+	sa->stop = ioc3aux_stop;
+	snprintf(sa->name, sizeof(sa->name), "IOC3 auxiliary %d", pdev->id);
+	snprintf(sa->phys, sizeof(sa->phys), "ioc3/serio%daux", pdev->id);
+	sa->port_data = d;
+	sa->dev.parent = dev;
+
+	d->regs = regs;
+	d->kbd = sk;
+	d->aux = sa;
+	d->irq = irq;
+
+	platform_set_drvdata(pdev, d);
+	serio_register_port(d->kbd);
+	serio_register_port(d->aux);
+
+	ret = request_irq(irq, ioc3kbd_intr, IRQF_SHARED, "ioc3-kbd", d);
+	if (ret) {
+		dev_err(dev, "could not request IRQ %d\n", irq);
+		serio_unregister_port(d->kbd);
+		serio_unregister_port(d->aux);
+		return ret;
+	}
+
+	/* enable ports */
+	writel(KM_CSR_K_CLAMP_3 | KM_CSR_M_CLAMP_3, &regs->km_csr);
+
+	return 0;
+}
+
+static void ioc3kbd_remove(struct platform_device *pdev)
+{
+	struct ioc3kbd_data *d = platform_get_drvdata(pdev);
+
+	free_irq(d->irq, d);
+
+	serio_unregister_port(d->kbd);
+	serio_unregister_port(d->aux);
+}
+
+static const struct platform_device_id ioc3kbd_id_table[] = {
+	{ "ioc3-kbd", },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, ioc3kbd_id_table);
+
+static struct platform_driver ioc3kbd_driver = {
+	.probe          = ioc3kbd_probe,
+	.remove         = ioc3kbd_remove,
+	.id_table	= ioc3kbd_id_table,
+	.driver = {
+		.name = "ioc3-kbd",
+	},
+};
+module_platform_driver(ioc3kbd_driver);
+
+MODULE_AUTHOR("Thomas Bogendoerfer <tbogendoerfer@suse.de>");
+MODULE_DESCRIPTION("SGI IOC3 serio driver");
+MODULE_LICENSE("GPL");