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, 253 insertions, 0 deletions

diff --git a/sound/soc/codecs/rl6231.c b/sound/soc/codecs/rl6231.c
new file mode 100644
index 000000000..d1fc17064
--- /dev/null
+++ b/sound/soc/codecs/rl6231.c
@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * rl6231.c - RL6231 class device shared support
+ *
+ * Copyright 2014 Realtek Semiconductor Corp.
+ *
+ * Author: Oder Chiou <oder_chiou@realtek.com>
+ */
+
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <linux/gcd.h>
+#include "rl6231.h"
+
+/**
+ * rl6231_get_pre_div - Return the value of pre divider.
+ *
+ * @map: map for setting.
+ * @reg: register.
+ * @sft: shift.
+ *
+ * Return the value of pre divider from given register value.
+ * Return negative error code for unexpected register value.
+ */
+int rl6231_get_pre_div(struct regmap *map, unsigned int reg, int sft)
+{
+	int pd, val;
+
+	regmap_read(map, reg, &val);
+
+	val = (val >> sft) & 0x7;
+
+	switch (val) {
+	case 0:
+	case 1:
+	case 2:
+	case 3:
+		pd = val + 1;
+		break;
+	case 4:
+		pd = 6;
+		break;
+	case 5:
+		pd = 8;
+		break;
+	case 6:
+		pd = 12;
+		break;
+	case 7:
+		pd = 16;
+		break;
+	default:
+		pd = -EINVAL;
+		break;
+	}
+
+	return pd;
+}
+EXPORT_SYMBOL_GPL(rl6231_get_pre_div);
+
+/**
+ * rl6231_calc_dmic_clk - Calculate the frequency divider parameter of dmic.
+ *
+ * @rate: base clock rate.
+ *
+ * Choose divider parameter that gives the highest possible DMIC frequency in
+ * 1MHz - 3MHz range.
+ */
+int rl6231_calc_dmic_clk(int rate)
+{
+	static const int div[] = {2, 3, 4, 6, 8, 12};
+	int i;
+
+	if (rate < 1000000 * div[0]) {
+		pr_warn("Base clock rate %d is too low\n", rate);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(div); i++) {
+		if ((div[i] % 3) == 0)
+			continue;
+		/* find divider that gives DMIC frequency below 1.536MHz */
+		if (1536000 * div[i] >= rate)
+			return i;
+	}
+
+	pr_warn("Base clock rate %d is too high\n", rate);
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(rl6231_calc_dmic_clk);
+
+struct pll_calc_map {
+	unsigned int pll_in;
+	unsigned int pll_out;
+	int k;
+	int n;
+	int m;
+	bool m_bp;
+	bool k_bp;
+};
+
+static const struct pll_calc_map pll_preset_table[] = {
+	{19200000,  4096000,  23, 14, 1, false, false},
+	{19200000,  24576000,  3, 30, 3, false, false},
+	{48000000,  3840000,  23,  2, 0, false, false},
+	{3840000,   24576000,  3, 30, 0, true, false},
+	{3840000,   22579200,  3,  5, 0, true, false},
+};
+
+static unsigned int find_best_div(unsigned int in,
+	unsigned int max, unsigned int div)
+{
+	unsigned int d;
+
+	if (in <= max)
+		return 1;
+
+	d = in / max;
+	if (in % max)
+		d++;
+
+	while (div % d != 0)
+		d++;
+
+
+	return d;
+}
+
+/**
+ * rl6231_pll_calc - Calcualte PLL M/N/K code.
+ * @freq_in: external clock provided to codec.
+ * @freq_out: target clock which codec works on.
+ * @pll_code: Pointer to structure with M, N, K, m_bypass and k_bypass flag.
+ *
+ * Calcualte M/N/K code to configure PLL for codec.
+ *
+ * Returns 0 for success or negative error code.
+ */
+int rl6231_pll_calc(const unsigned int freq_in,
+	const unsigned int freq_out, struct rl6231_pll_code *pll_code)
+{
+	int max_n = RL6231_PLL_N_MAX, max_m = RL6231_PLL_M_MAX;
+	int i, k, n_t;
+	int k_t, min_k, max_k, n = 0, m = 0, m_t = 0;
+	unsigned int red, pll_out, in_t, out_t, div, div_t;
+	unsigned int red_t = abs(freq_out - freq_in);
+	unsigned int f_in, f_out, f_max;
+	bool m_bypass = false, k_bypass = false;
+
+	if (RL6231_PLL_INP_MAX < freq_in || RL6231_PLL_INP_MIN > freq_in)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(pll_preset_table); i++) {
+		if (freq_in == pll_preset_table[i].pll_in &&
+			freq_out == pll_preset_table[i].pll_out) {
+			k = pll_preset_table[i].k;
+			m = pll_preset_table[i].m;
+			n = pll_preset_table[i].n;
+			m_bypass = pll_preset_table[i].m_bp;
+			k_bypass = pll_preset_table[i].k_bp;
+			pr_debug("Use preset PLL parameter table\n");
+			goto code_find;
+		}
+	}
+
+	min_k = 80000000 / freq_out - 2;
+	max_k = 150000000 / freq_out - 2;
+	if (max_k > RL6231_PLL_K_MAX)
+		max_k = RL6231_PLL_K_MAX;
+	if (min_k > RL6231_PLL_K_MAX)
+		min_k = max_k = RL6231_PLL_K_MAX;
+	div_t = gcd(freq_in, freq_out);
+	f_max = 0xffffffff / RL6231_PLL_N_MAX;
+	div = find_best_div(freq_in, f_max, div_t);
+	f_in = freq_in / div;
+	f_out = freq_out / div;
+	k = min_k;
+	if (min_k < -1)
+		min_k = -1;
+	for (k_t = min_k; k_t <= max_k; k_t++) {
+		for (n_t = 0; n_t <= max_n; n_t++) {
+			in_t = f_in * (n_t + 2);
+			pll_out = f_out * (k_t + 2);
+			if (in_t == pll_out) {
+				m_bypass = true;
+				n = n_t;
+				k = k_t;
+				goto code_find;
+			}
+			out_t = in_t / (k_t + 2);
+			red = abs(f_out - out_t);
+			if (red < red_t) {
+				m_bypass = true;
+				n = n_t;
+				m = 0;
+				k = k_t;
+				if (red == 0)
+					goto code_find;
+				red_t = red;
+			}
+			for (m_t = 0; m_t <= max_m; m_t++) {
+				out_t = in_t / ((m_t + 2) * (k_t + 2));
+				red = abs(f_out - out_t);
+				if (red < red_t) {
+					m_bypass = false;
+					n = n_t;
+					m = m_t;
+					k = k_t;
+					if (red == 0)
+						goto code_find;
+					red_t = red;
+				}
+			}
+		}
+	}
+	pr_debug("Only get approximation about PLL\n");
+
+code_find:
+	if (k == -1) {
+		k_bypass = true;
+		k = 0;
+	}
+
+	pll_code->m_bp = m_bypass;
+	pll_code->k_bp = k_bypass;
+	pll_code->m_code = m;
+	pll_code->n_code = n;
+	pll_code->k_code = k;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rl6231_pll_calc);
+
+int rl6231_get_clk_info(int sclk, int rate)
+{
+	int i;
+	static const int pd[] = {1, 2, 3, 4, 6, 8, 12, 16};
+
+	if (sclk <= 0 || rate <= 0)
+		return -EINVAL;
+
+	rate = rate << 8;
+	for (i = 0; i < ARRAY_SIZE(pd); i++)
+		if (sclk == rate * pd[i])
+			return i;
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(rl6231_get_clk_info);
+
+MODULE_DESCRIPTION("RL6231 class device shared support");
+MODULE_AUTHOR("Oder Chiou <oder_chiou@realtek.com>");
+MODULE_LICENSE("GPL v2");