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, 106 insertions, 0 deletions

diff --git a/drivers/clk/qcom/clk-regmap.c b/drivers/clk/qcom/clk-regmap.c
new file mode 100644
index 000000000..92ac4e0d7
--- /dev/null
+++ b/drivers/clk/qcom/clk-regmap.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2014, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/clk-provider.h>
+#include <linux/regmap.h>
+#include <linux/export.h>
+
+#include "clk-regmap.h"
+
+/**
+ * clk_is_enabled_regmap - standard is_enabled() for regmap users
+ *
+ * @hw: clk to operate on
+ *
+ * Clocks that use regmap for their register I/O can set the
+ * enable_reg and enable_mask fields in their struct clk_regmap and then use
+ * this as their is_enabled operation, saving some code.
+ */
+int clk_is_enabled_regmap(struct clk_hw *hw)
+{
+	struct clk_regmap *rclk = to_clk_regmap(hw);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_read(rclk->regmap, rclk->enable_reg, &val);
+	if (ret != 0)
+		return ret;
+
+	if (rclk->enable_is_inverted)
+		return (val & rclk->enable_mask) == 0;
+	else
+		return (val & rclk->enable_mask) != 0;
+}
+EXPORT_SYMBOL_GPL(clk_is_enabled_regmap);
+
+/**
+ * clk_enable_regmap - standard enable() for regmap users
+ *
+ * @hw: clk to operate on
+ *
+ * Clocks that use regmap for their register I/O can set the
+ * enable_reg and enable_mask fields in their struct clk_regmap and then use
+ * this as their enable() operation, saving some code.
+ */
+int clk_enable_regmap(struct clk_hw *hw)
+{
+	struct clk_regmap *rclk = to_clk_regmap(hw);
+	unsigned int val;
+
+	if (rclk->enable_is_inverted)
+		val = 0;
+	else
+		val = rclk->enable_mask;
+
+	return regmap_update_bits(rclk->regmap, rclk->enable_reg,
+				  rclk->enable_mask, val);
+}
+EXPORT_SYMBOL_GPL(clk_enable_regmap);
+
+/**
+ * clk_disable_regmap - standard disable() for regmap users
+ *
+ * @hw: clk to operate on
+ *
+ * Clocks that use regmap for their register I/O can set the
+ * enable_reg and enable_mask fields in their struct clk_regmap and then use
+ * this as their disable() operation, saving some code.
+ */
+void clk_disable_regmap(struct clk_hw *hw)
+{
+	struct clk_regmap *rclk = to_clk_regmap(hw);
+	unsigned int val;
+
+	if (rclk->enable_is_inverted)
+		val = rclk->enable_mask;
+	else
+		val = 0;
+
+	regmap_update_bits(rclk->regmap, rclk->enable_reg, rclk->enable_mask,
+			   val);
+}
+EXPORT_SYMBOL_GPL(clk_disable_regmap);
+
+/**
+ * devm_clk_register_regmap - register a clk_regmap clock
+ *
+ * @dev: reference to the caller's device
+ * @rclk: clk to operate on
+ *
+ * Clocks that use regmap for their register I/O should register their
+ * clk_regmap struct via this function so that the regmap is initialized
+ * and so that the clock is registered with the common clock framework.
+ */
+int devm_clk_register_regmap(struct device *dev, struct clk_regmap *rclk)
+{
+	if (dev && dev_get_regmap(dev, NULL))
+		rclk->regmap = dev_get_regmap(dev, NULL);
+	else if (dev && dev->parent)
+		rclk->regmap = dev_get_regmap(dev->parent, NULL);
+
+	return devm_clk_hw_register(dev, &rclk->hw);
+}
+EXPORT_SYMBOL_GPL(devm_clk_register_regmap);