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/sound/drivers/pcsp/pcsp.c b/sound/drivers/pcsp/pcsp.c
new file mode 100644
index 000000000..ff6bb375c
--- /dev/null
+++ b/sound/drivers/pcsp/pcsp.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PC-Speaker driver for Linux
+ *
+ * Copyright (C) 1997-2001  David Woodhouse
+ * Copyright (C) 2001-2008  Stas Sergeev
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include <sound/pcm.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/bitops.h>
+#include <linux/mm.h>
+#include "pcsp_input.h"
+#include "pcsp.h"
+
+MODULE_AUTHOR("Stas Sergeev <stsp@users.sourceforge.net>");
+MODULE_DESCRIPTION("PC-Speaker driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:pcspkr");
+
+static int index = SNDRV_DEFAULT_IDX1;	/* Index 0-MAX */
+static char *id = SNDRV_DEFAULT_STR1;	/* ID for this card */
+static bool enable = SNDRV_DEFAULT_ENABLE1;	/* Enable this card */
+static bool nopcm;	/* Disable PCM capability of the driver */
+
+module_param(index, int, 0444);
+MODULE_PARM_DESC(index, "Index value for pcsp soundcard.");
+module_param(id, charp, 0444);
+MODULE_PARM_DESC(id, "ID string for pcsp soundcard.");
+module_param(enable, bool, 0444);
+MODULE_PARM_DESC(enable, "Enable PC-Speaker sound.");
+module_param(nopcm, bool, 0444);
+MODULE_PARM_DESC(nopcm, "Disable PC-Speaker PCM sound. Only beeps remain.");
+
+struct snd_pcsp pcsp_chip;
+
+static int snd_pcsp_create(struct snd_card *card)
+{
+	unsigned int resolution = hrtimer_resolution;
+	int div, min_div, order;
+
+	if (!nopcm) {
+		if (resolution > PCSP_MAX_PERIOD_NS) {
+			dev_err(card->dev,
+				"PCSP: Timer resolution is not sufficient (%unS)\n",
+				resolution);
+			dev_err(card->dev,
+				"PCSP: Make sure you have HPET and ACPI enabled.\n");
+			dev_err(card->dev, "PCSP: Turned into nopcm mode.\n");
+			nopcm = 1;
+		}
+	}
+
+	if (loops_per_jiffy >= PCSP_MIN_LPJ && resolution <= PCSP_MIN_PERIOD_NS)
+		min_div = MIN_DIV;
+	else
+		min_div = MAX_DIV;
+#if PCSP_DEBUG
+	dev_dbg(card->dev, "PCSP: lpj=%li, min_div=%i, res=%u\n",
+		loops_per_jiffy, min_div, resolution);
+#endif
+
+	div = MAX_DIV / min_div;
+	order = fls(div) - 1;
+
+	pcsp_chip.max_treble = min(order, PCSP_MAX_TREBLE);
+	pcsp_chip.treble = min(pcsp_chip.max_treble, PCSP_DEFAULT_TREBLE);
+	pcsp_chip.playback_ptr = 0;
+	pcsp_chip.period_ptr = 0;
+	atomic_set(&pcsp_chip.timer_active, 0);
+	pcsp_chip.enable = 1;
+	pcsp_chip.pcspkr = 1;
+
+	spin_lock_init(&pcsp_chip.substream_lock);
+
+	pcsp_chip.card = card;
+	pcsp_chip.port = 0x61;
+	pcsp_chip.irq = -1;
+	pcsp_chip.dma = -1;
+	card->private_data = &pcsp_chip;
+
+	return 0;
+}
+
+static void pcsp_stop_beep(struct snd_pcsp *chip);
+
+static void alsa_card_pcsp_free(struct snd_card *card)
+{
+	pcsp_stop_beep(card->private_data);
+}
+
+static int snd_card_pcsp_probe(int devnum, struct device *dev)
+{
+	struct snd_card *card;
+	int err;
+
+	if (devnum != 0)
+		return -EINVAL;
+
+	hrtimer_setup(&pcsp_chip.timer, pcsp_do_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+
+	err = snd_devm_card_new(dev, index, id, THIS_MODULE, 0, &card);
+	if (err < 0)
+		return err;
+
+	err = snd_pcsp_create(card);
+	if (err < 0)
+		return err;
+
+	if (!nopcm) {
+		err = snd_pcsp_new_pcm(&pcsp_chip);
+		if (err < 0)
+			return err;
+	}
+	err = snd_pcsp_new_mixer(&pcsp_chip, nopcm);
+	if (err < 0)
+		return err;
+
+	strscpy(card->driver, "PC-Speaker");
+	strscpy(card->shortname, "pcsp");
+	sprintf(card->longname, "Internal PC-Speaker at port 0x%x",
+		pcsp_chip.port);
+
+	err = snd_card_register(card);
+	if (err < 0)
+		return err;
+	card->private_free = alsa_card_pcsp_free;
+
+	return 0;
+}
+
+static int alsa_card_pcsp_init(struct device *dev)
+{
+	int err;
+
+	err = snd_card_pcsp_probe(0, dev);
+	if (err) {
+		dev_err(dev, "PC-Speaker initialization failed.\n");
+		return err;
+	}
+
+	/* Well, CONFIG_DEBUG_PAGEALLOC makes the sound horrible. Lets alert */
+	if (debug_pagealloc_enabled()) {
+		dev_warn(dev,
+			 "PCSP: CONFIG_DEBUG_PAGEALLOC is enabled, which may make the sound noisy.\n");
+	}
+
+	return 0;
+}
+
+static int pcsp_probe(struct platform_device *dev)
+{
+	int err;
+
+	err = pcspkr_input_init(&pcsp_chip.input_dev, &dev->dev);
+	if (err < 0)
+		return err;
+
+	err = alsa_card_pcsp_init(&dev->dev);
+	if (err < 0)
+		return err;
+
+	platform_set_drvdata(dev, &pcsp_chip);
+	return 0;
+}
+
+static void pcsp_stop_beep(struct snd_pcsp *chip)
+{
+	pcsp_sync_stop(chip);
+	pcspkr_stop_sound();
+}
+
+static int pcsp_suspend(struct device *dev)
+{
+	struct snd_pcsp *chip = dev_get_drvdata(dev);
+	pcsp_stop_beep(chip);
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(pcsp_pm, pcsp_suspend, NULL);
+
+static void pcsp_shutdown(struct platform_device *dev)
+{
+	struct snd_pcsp *chip = platform_get_drvdata(dev);
+	pcsp_stop_beep(chip);
+}
+
+static struct platform_driver pcsp_platform_driver = {
+	.driver		= {
+		.name	= "pcspkr",
+		.pm	= &pcsp_pm,
+	},
+	.probe		= pcsp_probe,
+	.shutdown	= pcsp_shutdown,
+};
+
+static int __init pcsp_init(void)
+{
+	if (!enable)
+		return -ENODEV;
+	return platform_driver_register(&pcsp_platform_driver);
+}
+
+static void __exit pcsp_exit(void)
+{
+	platform_driver_unregister(&pcsp_platform_driver);
+}
+
+module_init(pcsp_init);
+module_exit(pcsp_exit);