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, 240 insertions, 0 deletions

diff --git a/drivers/media/rc/ir-sony-decoder.c b/drivers/media/rc/ir-sony-decoder.c
new file mode 100644
index 000000000..bb25867ec
--- /dev/null
+++ b/drivers/media/rc/ir-sony-decoder.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* ir-sony-decoder.c - handle Sony IR Pulse/Space protocol
+ *
+ * Copyright (C) 2010 by David Härdeman <david@hardeman.nu>
+ */
+
+#include <linux/bitrev.h>
+#include <linux/module.h>
+#include "rc-core-priv.h"
+
+#define SONY_UNIT		600 /* us */
+#define SONY_HEADER_PULSE	(4 * SONY_UNIT)
+#define	SONY_HEADER_SPACE	(1 * SONY_UNIT)
+#define SONY_BIT_0_PULSE	(1 * SONY_UNIT)
+#define SONY_BIT_1_PULSE	(2 * SONY_UNIT)
+#define SONY_BIT_SPACE		(1 * SONY_UNIT)
+#define SONY_TRAILER_SPACE	(10 * SONY_UNIT) /* minimum */
+
+enum sony_state {
+	STATE_INACTIVE,
+	STATE_HEADER_SPACE,
+	STATE_BIT_PULSE,
+	STATE_BIT_SPACE,
+	STATE_FINISHED,
+};
+
+/**
+ * ir_sony_decode() - Decode one Sony pulse or space
+ * @dev:	the struct rc_dev descriptor of the device
+ * @ev:         the struct ir_raw_event descriptor of the pulse/space
+ *
+ * This function returns -EINVAL if the pulse violates the state machine
+ */
+static int ir_sony_decode(struct rc_dev *dev, struct ir_raw_event ev)
+{
+	struct sony_dec *data = &dev->raw->sony;
+	enum rc_proto protocol;
+	u32 scancode;
+	u8 device, subdevice, function;
+
+	if (!is_timing_event(ev)) {
+		if (ev.overflow)
+			data->state = STATE_INACTIVE;
+		return 0;
+	}
+
+	if (!geq_margin(ev.duration, SONY_UNIT, SONY_UNIT / 2))
+		goto out;
+
+	dev_dbg(&dev->dev, "Sony decode started at state %d (%uus %s)\n",
+		data->state, ev.duration, TO_STR(ev.pulse));
+
+	switch (data->state) {
+
+	case STATE_INACTIVE:
+		if (!ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, SONY_HEADER_PULSE, SONY_UNIT / 2))
+			break;
+
+		data->count = 0;
+		data->state = STATE_HEADER_SPACE;
+		return 0;
+
+	case STATE_HEADER_SPACE:
+		if (ev.pulse)
+			break;
+
+		if (!eq_margin(ev.duration, SONY_HEADER_SPACE, SONY_UNIT / 2))
+			break;
+
+		data->state = STATE_BIT_PULSE;
+		return 0;
+
+	case STATE_BIT_PULSE:
+		if (!ev.pulse)
+			break;
+
+		data->bits <<= 1;
+		if (eq_margin(ev.duration, SONY_BIT_1_PULSE, SONY_UNIT / 2))
+			data->bits |= 1;
+		else if (!eq_margin(ev.duration, SONY_BIT_0_PULSE, SONY_UNIT / 2))
+			break;
+
+		data->count++;
+		data->state = STATE_BIT_SPACE;
+		return 0;
+
+	case STATE_BIT_SPACE:
+		if (ev.pulse)
+			break;
+
+		if (!geq_margin(ev.duration, SONY_BIT_SPACE, SONY_UNIT / 2))
+			break;
+
+		decrease_duration(&ev, SONY_BIT_SPACE);
+
+		if (!geq_margin(ev.duration, SONY_UNIT, SONY_UNIT / 2)) {
+			data->state = STATE_BIT_PULSE;
+			return 0;
+		}
+
+		data->state = STATE_FINISHED;
+		fallthrough;
+
+	case STATE_FINISHED:
+		if (ev.pulse)
+			break;
+
+		if (!geq_margin(ev.duration, SONY_TRAILER_SPACE, SONY_UNIT / 2))
+			break;
+
+		switch (data->count) {
+		case 12:
+			if (!(dev->enabled_protocols & RC_PROTO_BIT_SONY12))
+				goto finish_state_machine;
+
+			device    = bitrev8((data->bits <<  3) & 0xF8);
+			subdevice = 0;
+			function  = bitrev8((data->bits >>  4) & 0xFE);
+			protocol = RC_PROTO_SONY12;
+			break;
+		case 15:
+			if (!(dev->enabled_protocols & RC_PROTO_BIT_SONY15))
+				goto finish_state_machine;
+
+			device    = bitrev8((data->bits >>  0) & 0xFF);
+			subdevice = 0;
+			function  = bitrev8((data->bits >>  7) & 0xFE);
+			protocol = RC_PROTO_SONY15;
+			break;
+		case 20:
+			if (!(dev->enabled_protocols & RC_PROTO_BIT_SONY20))
+				goto finish_state_machine;
+
+			device    = bitrev8((data->bits >>  5) & 0xF8);
+			subdevice = bitrev8((data->bits >>  0) & 0xFF);
+			function  = bitrev8((data->bits >> 12) & 0xFE);
+			protocol = RC_PROTO_SONY20;
+			break;
+		default:
+			dev_dbg(&dev->dev, "Sony invalid bitcount %u\n",
+				data->count);
+			goto out;
+		}
+
+		scancode = device << 16 | subdevice << 8 | function;
+		dev_dbg(&dev->dev, "Sony(%u) scancode 0x%05x\n", data->count,
+			scancode);
+		rc_keydown(dev, protocol, scancode, 0);
+		goto finish_state_machine;
+	}
+
+out:
+	dev_dbg(&dev->dev, "Sony decode failed at state %d (%uus %s)\n",
+		data->state, ev.duration, TO_STR(ev.pulse));
+	data->state = STATE_INACTIVE;
+	return -EINVAL;
+
+finish_state_machine:
+	data->state = STATE_INACTIVE;
+	return 0;
+}
+
+static const struct ir_raw_timings_pl ir_sony_timings = {
+	.header_pulse  = SONY_HEADER_PULSE,
+	.bit_space     = SONY_BIT_SPACE,
+	.bit_pulse[0]  = SONY_BIT_0_PULSE,
+	.bit_pulse[1]  = SONY_BIT_1_PULSE,
+	.trailer_space = SONY_TRAILER_SPACE + SONY_BIT_SPACE,
+	.msb_first     = 0,
+};
+
+/**
+ * ir_sony_encode() - Encode a scancode as a stream of raw events
+ *
+ * @protocol:	protocol to encode
+ * @scancode:	scancode to encode
+ * @events:	array of raw ir events to write into
+ * @max:	maximum size of @events
+ *
+ * Returns:	The number of events written.
+ *		-ENOBUFS if there isn't enough space in the array to fit the
+ *		encoding. In this case all @max events will have been written.
+ */
+static int ir_sony_encode(enum rc_proto protocol, u32 scancode,
+			  struct ir_raw_event *events, unsigned int max)
+{
+	struct ir_raw_event *e = events;
+	u32 raw, len;
+	int ret;
+
+	if (protocol == RC_PROTO_SONY12) {
+		raw = (scancode & 0x7f) | ((scancode & 0x1f0000) >> 9);
+		len = 12;
+	} else if (protocol == RC_PROTO_SONY15) {
+		raw = (scancode & 0x7f) | ((scancode & 0xff0000) >> 9);
+		len = 15;
+	} else {
+		raw = (scancode & 0x7f) | ((scancode & 0x1f0000) >> 9) |
+		       ((scancode & 0xff00) << 4);
+		len = 20;
+	}
+
+	ret = ir_raw_gen_pl(&e, max, &ir_sony_timings, len, raw);
+	if (ret < 0)
+		return ret;
+
+	return e - events;
+}
+
+static struct ir_raw_handler sony_handler = {
+	.protocols	= RC_PROTO_BIT_SONY12 | RC_PROTO_BIT_SONY15 |
+							RC_PROTO_BIT_SONY20,
+	.decode		= ir_sony_decode,
+	.encode		= ir_sony_encode,
+	.carrier	= 40000,
+	.min_timeout	= SONY_TRAILER_SPACE,
+};
+
+static int __init ir_sony_decode_init(void)
+{
+	ir_raw_handler_register(&sony_handler);
+
+	printk(KERN_INFO "IR Sony protocol handler initialized\n");
+	return 0;
+}
+
+static void __exit ir_sony_decode_exit(void)
+{
+	ir_raw_handler_unregister(&sony_handler);
+}
+
+module_init(ir_sony_decode_init);
+module_exit(ir_sony_decode_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Härdeman <david@hardeman.nu>");
+MODULE_DESCRIPTION("Sony IR protocol decoder");