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, 266 insertions, 0 deletions

diff --git a/sound/firewire/fireface/ff.c b/sound/firewire/fireface/ff.c
new file mode 100644
index 000000000..13472822d
--- /dev/null
+++ b/sound/firewire/fireface/ff.c
@@ -0,0 +1,266 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ff.c - a part of driver for RME Fireface series
+ *
+ * Copyright (c) 2015-2017 Takashi Sakamoto
+ */
+
+#include "ff.h"
+
+#define OUI_RME	0x000a35
+
+MODULE_DESCRIPTION("RME Fireface series Driver");
+MODULE_AUTHOR("Takashi Sakamoto <o-takashi@sakamocchi.jp>");
+MODULE_LICENSE("GPL");
+
+static void name_card(struct snd_ff *ff)
+{
+	struct fw_device *fw_dev = fw_parent_device(ff->unit);
+	static const char *const names[] = {
+		[SND_FF_UNIT_VERSION_FF800]	= "Fireface800",
+		[SND_FF_UNIT_VERSION_FF400]	= "Fireface400",
+		[SND_FF_UNIT_VERSION_UFX]	= "FirefaceUFX",
+		[SND_FF_UNIT_VERSION_UCX]	= "FirefaceUCX",
+		[SND_FF_UNIT_VERSION_802]	= "Fireface802",
+	};
+	const char *name;
+
+	name = names[ff->unit_version];
+
+	strscpy(ff->card->driver, "Fireface");
+	strscpy(ff->card->shortname, name);
+	strscpy(ff->card->mixername, name);
+	snprintf(ff->card->longname, sizeof(ff->card->longname),
+		 "RME %s, GUID %08x%08x at %s, S%d", name,
+		 fw_dev->config_rom[3], fw_dev->config_rom[4],
+		 dev_name(&ff->unit->device), 100 << fw_dev->max_speed);
+}
+
+static void ff_card_free(struct snd_card *card)
+{
+	struct snd_ff *ff = card->private_data;
+
+	snd_ff_stream_destroy_duplex(ff);
+	snd_ff_transaction_unregister(ff);
+
+	kfree(ff->msg_parser);
+
+	mutex_destroy(&ff->mutex);
+	fw_unit_put(ff->unit);
+}
+
+static int snd_ff_probe(struct fw_unit *unit, const struct ieee1394_device_id *entry)
+{
+	struct snd_card *card;
+	struct snd_ff *ff;
+	int err;
+
+	err = snd_card_new(&unit->device, -1, NULL, THIS_MODULE, sizeof(*ff), &card);
+	if (err < 0)
+		return err;
+	card->private_free = ff_card_free;
+
+	ff = card->private_data;
+	ff->unit = fw_unit_get(unit);
+	dev_set_drvdata(&unit->device, ff);
+	ff->card = card;
+
+	mutex_init(&ff->mutex);
+	spin_lock_init(&ff->lock);
+	init_waitqueue_head(&ff->hwdep_wait);
+
+	ff->unit_version = entry->version;
+	ff->spec = entry->driver_data_ptr;
+
+	err = snd_ff_transaction_register(ff);
+	if (err < 0)
+		goto error;
+
+	name_card(ff);
+
+	err = snd_ff_stream_init_duplex(ff);
+	if (err < 0)
+		goto error;
+
+	snd_ff_proc_init(ff);
+
+	err = snd_ff_create_midi_devices(ff);
+	if (err < 0)
+		goto error;
+
+	err = snd_ff_create_pcm_devices(ff);
+	if (err < 0)
+		goto error;
+
+	err = snd_ff_create_hwdep_devices(ff);
+	if (err < 0)
+		goto error;
+
+	if (ff->spec->protocol->msg_parser_size > 0) {
+		ff->msg_parser = kzalloc(ff->spec->protocol->msg_parser_size, GFP_KERNEL);
+		if (!ff->msg_parser) {
+			err = -ENOMEM;
+			goto error;
+		}
+	}
+
+	err = snd_card_register(card);
+	if (err < 0)
+		goto error;
+
+	return 0;
+error:
+	snd_card_free(card);
+	return err;
+}
+
+static void snd_ff_update(struct fw_unit *unit)
+{
+	struct snd_ff *ff = dev_get_drvdata(&unit->device);
+
+	snd_ff_transaction_reregister(ff);
+
+	snd_ff_stream_update_duplex(ff);
+}
+
+static void snd_ff_remove(struct fw_unit *unit)
+{
+	struct snd_ff *ff = dev_get_drvdata(&unit->device);
+
+	// Block till all of ALSA character devices are released.
+	snd_card_free(ff->card);
+}
+
+static const struct snd_ff_spec spec_ff800 = {
+	.pcm_capture_channels = {28, 20, 12},
+	.pcm_playback_channels = {28, 20, 12},
+	.midi_in_ports = 1,
+	.midi_out_ports = 1,
+	.protocol = &snd_ff_protocol_ff800,
+	.midi_high_addr = 0x000200000320ull,
+	.midi_addr_range = 12,
+	.midi_rx_addrs = {0x000080180000ull, 0},
+};
+
+static const struct snd_ff_spec spec_ff400 = {
+	.pcm_capture_channels = {18, 14, 10},
+	.pcm_playback_channels = {18, 14, 10},
+	.midi_in_ports = 2,
+	.midi_out_ports = 2,
+	.protocol = &snd_ff_protocol_ff400,
+	.midi_high_addr = 0x0000801003f4ull,
+	.midi_addr_range = SND_FF_MAXIMIM_MIDI_QUADS * 4,
+	.midi_rx_addrs = {0x000080180000ull, 0x000080190000ull},
+};
+
+static const struct snd_ff_spec spec_ucx = {
+	.pcm_capture_channels = {18, 14, 12},
+	.pcm_playback_channels = {18, 14, 12},
+	.midi_in_ports = 2,
+	.midi_out_ports = 2,
+	.protocol = &snd_ff_protocol_latter,
+	.midi_high_addr = 0xffff00000034ull,
+	.midi_addr_range = 0x80,
+	.midi_rx_addrs = {0xffff00000030ull, 0xffff00000030ull},
+};
+
+static const struct snd_ff_spec spec_ufx_802 = {
+	.pcm_capture_channels = {30, 22, 14},
+	.pcm_playback_channels = {30, 22, 14},
+	.midi_in_ports = 1,
+	.midi_out_ports = 1,
+	.protocol = &snd_ff_protocol_latter,
+	.midi_high_addr = 0xffff00000034ull,
+	.midi_addr_range = 0x80,
+	.midi_rx_addrs = {0xffff00000030ull, 0xffff00000030ull},
+};
+
+static const struct ieee1394_device_id snd_ff_id_table[] = {
+	/* Fireface 800 */
+	{
+		.match_flags	= IEEE1394_MATCH_VENDOR_ID |
+				  IEEE1394_MATCH_SPECIFIER_ID |
+				  IEEE1394_MATCH_VERSION |
+				  IEEE1394_MATCH_MODEL_ID,
+		.vendor_id	= OUI_RME,
+		.specifier_id	= OUI_RME,
+		.version	= SND_FF_UNIT_VERSION_FF800,
+		.model_id	= 0x101800,
+		.driver_data_ptr = &spec_ff800,
+	},
+	/* Fireface 400 */
+	{
+		.match_flags	= IEEE1394_MATCH_VENDOR_ID |
+				  IEEE1394_MATCH_SPECIFIER_ID |
+				  IEEE1394_MATCH_VERSION |
+				  IEEE1394_MATCH_MODEL_ID,
+		.vendor_id	= OUI_RME,
+		.specifier_id	= OUI_RME,
+		.version	= SND_FF_UNIT_VERSION_FF400,
+		.model_id	= 0x101800,
+		.driver_data_ptr = &spec_ff400,
+	},
+	// Fireface UFX.
+	{
+		.match_flags	= IEEE1394_MATCH_VENDOR_ID |
+				  IEEE1394_MATCH_SPECIFIER_ID |
+				  IEEE1394_MATCH_VERSION |
+				  IEEE1394_MATCH_MODEL_ID,
+		.vendor_id	= OUI_RME,
+		.specifier_id	= OUI_RME,
+		.version	= SND_FF_UNIT_VERSION_UFX,
+		.model_id	= 0x101800,
+		.driver_data_ptr = &spec_ufx_802,
+	},
+	// Fireface UCX.
+	{
+		.match_flags	= IEEE1394_MATCH_VENDOR_ID |
+				  IEEE1394_MATCH_SPECIFIER_ID |
+				  IEEE1394_MATCH_VERSION |
+				  IEEE1394_MATCH_MODEL_ID,
+		.vendor_id	= OUI_RME,
+		.specifier_id	= OUI_RME,
+		.version	= SND_FF_UNIT_VERSION_UCX,
+		.model_id	= 0x101800,
+		.driver_data_ptr = &spec_ucx,
+	},
+	// Fireface 802.
+	{
+		.match_flags	= IEEE1394_MATCH_VENDOR_ID |
+				  IEEE1394_MATCH_SPECIFIER_ID |
+				  IEEE1394_MATCH_VERSION |
+				  IEEE1394_MATCH_MODEL_ID,
+		.vendor_id	= OUI_RME,
+		.specifier_id	= OUI_RME,
+		.version	= SND_FF_UNIT_VERSION_802,
+		.model_id	= 0x101800,
+		.driver_data_ptr = &spec_ufx_802,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(ieee1394, snd_ff_id_table);
+
+static struct fw_driver ff_driver = {
+	.driver = {
+		.owner	= THIS_MODULE,
+		.name	= KBUILD_MODNAME,
+		.bus	= &fw_bus_type,
+	},
+	.probe    = snd_ff_probe,
+	.update   = snd_ff_update,
+	.remove   = snd_ff_remove,
+	.id_table = snd_ff_id_table,
+};
+
+static int __init snd_ff_init(void)
+{
+	return driver_register(&ff_driver.driver);
+}
+
+static void __exit snd_ff_exit(void)
+{
+	driver_unregister(&ff_driver.driver);
+}
+
+module_init(snd_ff_init);
+module_exit(snd_ff_exit);