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, 157 insertions, 0 deletions

diff --git a/drivers/hwspinlock/sprd_hwspinlock.c b/drivers/hwspinlock/sprd_hwspinlock.c
new file mode 100644
index 000000000..22e2ffb91
--- /dev/null
+++ b/drivers/hwspinlock/sprd_hwspinlock.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Spreadtrum hardware spinlock driver
+ * Copyright (C) 2017 Spreadtrum  - http://www.spreadtrum.com
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/hwspinlock.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+
+#include "hwspinlock_internal.h"
+
+/* hwspinlock registers definition */
+#define HWSPINLOCK_RECCTRL		0x4
+#define HWSPINLOCK_MASTERID(_X_)	(0x80 + 0x4 * (_X_))
+#define HWSPINLOCK_TOKEN(_X_)		(0x800 + 0x4 * (_X_))
+
+/* unlocked value */
+#define HWSPINLOCK_NOTTAKEN		0x55aa10c5
+/* bits definition of RECCTRL reg */
+#define HWSPINLOCK_USER_BITS		0x1
+
+/* hwspinlock number */
+#define SPRD_HWLOCKS_NUM		32
+
+struct sprd_hwspinlock_dev {
+	void __iomem *base;
+	struct clk *clk;
+	struct hwspinlock_device bank;
+};
+
+/* try to lock the hardware spinlock */
+static int sprd_hwspinlock_trylock(struct hwspinlock *lock)
+{
+	struct sprd_hwspinlock_dev *sprd_hwlock =
+		dev_get_drvdata(lock->bank->dev);
+	void __iomem *addr = lock->priv;
+	int user_id, lock_id;
+
+	if (!readl(addr))
+		return 1;
+
+	lock_id = hwlock_to_id(lock);
+	/* get the hardware spinlock master/user id */
+	user_id = readl(sprd_hwlock->base + HWSPINLOCK_MASTERID(lock_id));
+	dev_warn(sprd_hwlock->bank.dev,
+		 "hwspinlock [%d] lock failed and master/user id = %d!\n",
+		 lock_id, user_id);
+	return 0;
+}
+
+/* unlock the hardware spinlock */
+static void sprd_hwspinlock_unlock(struct hwspinlock *lock)
+{
+	void __iomem *lock_addr = lock->priv;
+
+	writel(HWSPINLOCK_NOTTAKEN, lock_addr);
+}
+
+/* The specs recommended below number as the retry delay time */
+static void sprd_hwspinlock_relax(struct hwspinlock *lock)
+{
+	ndelay(10);
+}
+
+static const struct hwspinlock_ops sprd_hwspinlock_ops = {
+	.trylock = sprd_hwspinlock_trylock,
+	.unlock = sprd_hwspinlock_unlock,
+	.relax = sprd_hwspinlock_relax,
+};
+
+static void sprd_hwspinlock_disable(void *data)
+{
+	struct sprd_hwspinlock_dev *sprd_hwlock = data;
+
+	clk_disable_unprepare(sprd_hwlock->clk);
+}
+
+static int sprd_hwspinlock_probe(struct platform_device *pdev)
+{
+	struct sprd_hwspinlock_dev *sprd_hwlock;
+	struct hwspinlock *lock;
+	int i, ret;
+
+	if (!pdev->dev.of_node)
+		return -ENODEV;
+
+	sprd_hwlock = devm_kzalloc(&pdev->dev,
+				   struct_size(sprd_hwlock, bank.lock, SPRD_HWLOCKS_NUM),
+				   GFP_KERNEL);
+	if (!sprd_hwlock)
+		return -ENOMEM;
+
+	sprd_hwlock->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(sprd_hwlock->base))
+		return PTR_ERR(sprd_hwlock->base);
+
+	sprd_hwlock->clk = devm_clk_get(&pdev->dev, "enable");
+	if (IS_ERR(sprd_hwlock->clk)) {
+		dev_err(&pdev->dev, "get hwspinlock clock failed!\n");
+		return PTR_ERR(sprd_hwlock->clk);
+	}
+
+	ret = clk_prepare_enable(sprd_hwlock->clk);
+	if (ret)
+		return ret;
+
+	ret = devm_add_action_or_reset(&pdev->dev, sprd_hwspinlock_disable,
+				       sprd_hwlock);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"Failed to add hwspinlock disable action\n");
+		return ret;
+	}
+
+	/* set the hwspinlock to record user id to identify subsystems */
+	writel(HWSPINLOCK_USER_BITS, sprd_hwlock->base + HWSPINLOCK_RECCTRL);
+
+	for (i = 0; i < SPRD_HWLOCKS_NUM; i++) {
+		lock = &sprd_hwlock->bank.lock[i];
+		lock->priv = sprd_hwlock->base + HWSPINLOCK_TOKEN(i);
+	}
+
+	platform_set_drvdata(pdev, sprd_hwlock);
+
+	return devm_hwspin_lock_register(&pdev->dev, &sprd_hwlock->bank,
+					 &sprd_hwspinlock_ops, 0,
+					 SPRD_HWLOCKS_NUM);
+}
+
+static const struct of_device_id sprd_hwspinlock_of_match[] = {
+	{ .compatible = "sprd,hwspinlock-r3p0", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, sprd_hwspinlock_of_match);
+
+static struct platform_driver sprd_hwspinlock_driver = {
+	.probe = sprd_hwspinlock_probe,
+	.driver = {
+		.name = "sprd_hwspinlock",
+		.of_match_table = sprd_hwspinlock_of_match,
+	},
+};
+module_platform_driver(sprd_hwspinlock_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Hardware spinlock driver for Spreadtrum");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@spreadtrum.com>");
+MODULE_AUTHOR("Lanqing Liu <lanqing.liu@spreadtrum.com>");
+MODULE_AUTHOR("Long Cheng <aiden.cheng@spreadtrum.com>");