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, 90 insertions, 0 deletions

diff --git a/drivers/base/regmap/regmap-ac97.c b/drivers/base/regmap/regmap-ac97.c
new file mode 100644
index 000000000..a561971c4
--- /dev/null
+++ b/drivers/base/regmap/regmap-ac97.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// Register map access API - AC'97 support
+//
+// Copyright 2013 Linaro Ltd.  All rights reserved.
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <sound/ac97_codec.h>
+
+bool regmap_ac97_default_volatile(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case AC97_RESET:
+	case AC97_POWERDOWN:
+	case AC97_INT_PAGING:
+	case AC97_EXTENDED_ID:
+	case AC97_EXTENDED_STATUS:
+	case AC97_EXTENDED_MID:
+	case AC97_EXTENDED_MSTATUS:
+	case AC97_GPIO_STATUS:
+	case AC97_MISC_AFE:
+	case AC97_VENDOR_ID1:
+	case AC97_VENDOR_ID2:
+	case AC97_CODEC_CLASS_REV:
+	case AC97_PCI_SVID:
+	case AC97_PCI_SID:
+	case AC97_FUNC_SELECT:
+	case AC97_FUNC_INFO:
+	case AC97_SENSE_INFO:
+		return true;
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(regmap_ac97_default_volatile);
+
+static int regmap_ac97_reg_read(void *context, unsigned int reg,
+	unsigned int *val)
+{
+	struct snd_ac97 *ac97 = context;
+
+	*val = ac97->bus->ops->read(ac97, reg);
+
+	return 0;
+}
+
+static int regmap_ac97_reg_write(void *context, unsigned int reg,
+	unsigned int val)
+{
+	struct snd_ac97 *ac97 = context;
+
+	ac97->bus->ops->write(ac97, reg, val);
+
+	return 0;
+}
+
+static const struct regmap_bus ac97_regmap_bus = {
+	.reg_write = regmap_ac97_reg_write,
+	.reg_read = regmap_ac97_reg_read,
+};
+
+struct regmap *__regmap_init_ac97(struct snd_ac97 *ac97,
+				  const struct regmap_config *config,
+				  struct lock_class_key *lock_key,
+				  const char *lock_name)
+{
+	return __regmap_init(&ac97->dev, &ac97_regmap_bus, ac97, config,
+			     lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__regmap_init_ac97);
+
+struct regmap *__devm_regmap_init_ac97(struct snd_ac97 *ac97,
+				       const struct regmap_config *config,
+				       struct lock_class_key *lock_key,
+				       const char *lock_name)
+{
+	return __devm_regmap_init(&ac97->dev, &ac97_regmap_bus, ac97, config,
+				  lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_ac97);
+
+MODULE_DESCRIPTION("Register map access API - AC'97 support");
+MODULE_LICENSE("GPL v2");