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, 190 insertions, 0 deletions

diff --git a/sound/ppc/powermac.c b/sound/ppc/powermac.c
new file mode 100644
index 000000000..e685d2458
--- /dev/null
+++ b/sound/ppc/powermac.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for PowerMac AWACS
+ * Copyright (c) 2001 by Takashi Iwai <tiwai@suse.de>
+ *   based on dmasound.c.
+ */
+
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <sound/core.h>
+#include <sound/initval.h>
+#include "pmac.h"
+#include "awacs.h"
+#include "burgundy.h"
+
+#define CHIP_NAME "PMac"
+
+MODULE_DESCRIPTION("PowerMac");
+MODULE_LICENSE("GPL");
+
+static int index = SNDRV_DEFAULT_IDX1;		/* Index 0-MAX */
+static char *id = SNDRV_DEFAULT_STR1;		/* ID for this card */
+static bool enable_beep = 1;
+
+module_param(index, int, 0444);
+MODULE_PARM_DESC(index, "Index value for " CHIP_NAME " soundchip.");
+module_param(id, charp, 0444);
+MODULE_PARM_DESC(id, "ID string for " CHIP_NAME " soundchip.");
+module_param(enable_beep, bool, 0444);
+MODULE_PARM_DESC(enable_beep, "Enable beep using PCM.");
+
+static struct platform_device *device;
+
+
+/*
+ */
+
+static int snd_pmac_probe(struct platform_device *devptr)
+{
+	struct snd_card *card;
+	struct snd_pmac *chip;
+	char *name_ext;
+	int err;
+
+	err = snd_card_new(&devptr->dev, index, id, THIS_MODULE, 0, &card);
+	if (err < 0)
+		return err;
+
+	err = snd_pmac_new(card, &chip);
+	if (err < 0)
+		goto __error;
+	card->private_data = chip;
+
+	switch (chip->model) {
+	case PMAC_BURGUNDY:
+		strscpy(card->driver, "PMac Burgundy");
+		strscpy(card->shortname, "PowerMac Burgundy");
+		sprintf(card->longname, "%s (Dev %d) Sub-frame %d",
+			card->shortname, chip->device_id, chip->subframe);
+		err = snd_pmac_burgundy_init(chip);
+		if (err < 0)
+			goto __error;
+		break;
+	case PMAC_DACA:
+		strscpy(card->driver, "PMac DACA");
+		strscpy(card->shortname, "PowerMac DACA");
+		sprintf(card->longname, "%s (Dev %d) Sub-frame %d",
+			card->shortname, chip->device_id, chip->subframe);
+		err = snd_pmac_daca_init(chip);
+		if (err < 0)
+			goto __error;
+		break;
+	case PMAC_TUMBLER:
+	case PMAC_SNAPPER:
+		name_ext = chip->model == PMAC_TUMBLER ? "Tumbler" : "Snapper";
+		sprintf(card->driver, "PMac %s", name_ext);
+		sprintf(card->shortname, "PowerMac %s", name_ext);
+		sprintf(card->longname, "%s (Dev %d) Sub-frame %d",
+			card->shortname, chip->device_id, chip->subframe);
+		err = snd_pmac_tumbler_init(chip);
+		if (err < 0)
+			goto __error;
+		err = snd_pmac_tumbler_post_init();
+		if (err < 0)
+			goto __error;
+		break;
+	case PMAC_AWACS:
+	case PMAC_SCREAMER:
+		name_ext = chip->model == PMAC_SCREAMER ? "Screamer" : "AWACS";
+		sprintf(card->driver, "PMac %s", name_ext);
+		sprintf(card->shortname, "PowerMac %s", name_ext);
+		if (chip->is_pbook_3400)
+			name_ext = " [PB3400]";
+		else if (chip->is_pbook_G3)
+			name_ext = " [PBG3]";
+		else
+			name_ext = "";
+		sprintf(card->longname, "%s%s Rev %d",
+			card->shortname, name_ext, chip->revision);
+		err = snd_pmac_awacs_init(chip);
+		if (err < 0)
+			goto __error;
+		break;
+	default:
+		dev_err(&devptr->dev, "unsupported hardware %d\n", chip->model);
+		err = -EINVAL;
+		goto __error;
+	}
+
+	err = snd_pmac_pcm_new(chip);
+	if (err < 0)
+		goto __error;
+
+	chip->initialized = 1;
+	if (enable_beep)
+		snd_pmac_attach_beep(chip);
+
+	err = snd_card_register(card);
+	if (err < 0)
+		goto __error;
+
+	platform_set_drvdata(devptr, card);
+	return 0;
+
+__error:
+	snd_card_free(card);
+	return err;
+}
+
+
+static void snd_pmac_remove(struct platform_device *devptr)
+{
+	snd_card_free(platform_get_drvdata(devptr));
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int snd_pmac_driver_suspend(struct device *dev)
+{
+	struct snd_card *card = dev_get_drvdata(dev);
+	snd_pmac_suspend(card->private_data);
+	return 0;
+}
+
+static int snd_pmac_driver_resume(struct device *dev)
+{
+	struct snd_card *card = dev_get_drvdata(dev);
+	snd_pmac_resume(card->private_data);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(snd_pmac_pm, snd_pmac_driver_suspend, snd_pmac_driver_resume);
+#define SND_PMAC_PM_OPS	&snd_pmac_pm
+#else
+#define SND_PMAC_PM_OPS	NULL
+#endif
+
+#define SND_PMAC_DRIVER		"snd_powermac"
+
+static struct platform_driver snd_pmac_driver = {
+	.probe		= snd_pmac_probe,
+	.remove		= snd_pmac_remove,
+	.driver		= {
+		.name	= SND_PMAC_DRIVER,
+		.pm	= SND_PMAC_PM_OPS,
+	},
+};
+
+static int __init alsa_card_pmac_init(void)
+{
+	int err;
+
+	err = platform_driver_register(&snd_pmac_driver);
+	if (err < 0)
+		return err;
+	device = platform_device_register_simple(SND_PMAC_DRIVER, -1, NULL, 0);
+	return 0;
+
+}
+
+static void __exit alsa_card_pmac_exit(void)
+{
+	if (!IS_ERR(device))
+		platform_device_unregister(device);
+	platform_driver_unregister(&snd_pmac_driver);
+}
+
+module_init(alsa_card_pmac_init)
+module_exit(alsa_card_pmac_exit)