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, 211 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/utstring.c b/drivers/acpi/acpica/utstring.c
new file mode 100644
index 000000000..aae71b8c5
--- /dev/null
+++ b/drivers/acpi/acpica/utstring.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*******************************************************************************
+ *
+ * Module Name: utstring - Common functions for strings and characters
+ *
+ ******************************************************************************/
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acnamesp.h"
+
+#define _COMPONENT          ACPI_UTILITIES
+ACPI_MODULE_NAME("utstring")
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_print_string
+ *
+ * PARAMETERS:  string          - Null terminated ASCII string
+ *              max_length      - Maximum output length. Used to constrain the
+ *                                length of strings during debug output only.
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Dump an ASCII string with support for ACPI-defined escape
+ *              sequences.
+ *
+ ******************************************************************************/
+void acpi_ut_print_string(char *string, u16 max_length)
+{
+	u32 i;
+
+	if (!string) {
+		acpi_os_printf("<\"NULL STRING PTR\">");
+		return;
+	}
+
+	acpi_os_printf("\"");
+	for (i = 0; (i < max_length) && string[i]; i++) {
+
+		/* Escape sequences */
+
+		switch (string[i]) {
+		case 0x07:
+
+			acpi_os_printf("\\a");	/* BELL */
+			break;
+
+		case 0x08:
+
+			acpi_os_printf("\\b");	/* BACKSPACE */
+			break;
+
+		case 0x0C:
+
+			acpi_os_printf("\\f");	/* FORMFEED */
+			break;
+
+		case 0x0A:
+
+			acpi_os_printf("\\n");	/* LINEFEED */
+			break;
+
+		case 0x0D:
+
+			acpi_os_printf("\\r");	/* CARRIAGE RETURN */
+			break;
+
+		case 0x09:
+
+			acpi_os_printf("\\t");	/* HORIZONTAL TAB */
+			break;
+
+		case 0x0B:
+
+			acpi_os_printf("\\v");	/* VERTICAL TAB */
+			break;
+
+		case '\'':	/* Single Quote */
+		case '\"':	/* Double Quote */
+		case '\\':	/* Backslash */
+
+			acpi_os_printf("\\%c", (int)string[i]);
+			break;
+
+		default:
+
+			/* Check for printable character or hex escape */
+
+			if (isprint((int)string[i])) {
+				/* This is a normal character */
+
+				acpi_os_printf("%c", (int)string[i]);
+			} else {
+				/* All others will be Hex escapes */
+
+				acpi_os_printf("\\x%2.2X", (s32)string[i]);
+			}
+			break;
+		}
+	}
+
+	acpi_os_printf("\"");
+
+	if (i == max_length && string[i]) {
+		acpi_os_printf("...");
+	}
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ut_repair_name
+ *
+ * PARAMETERS:  name            - The ACPI name to be repaired
+ *
+ * RETURN:      Repaired version of the name
+ *
+ * DESCRIPTION: Repair an ACPI name: Change invalid characters to '*' and
+ *              return the new name. NOTE: the Name parameter must reside in
+ *              read/write memory, cannot be a const.
+ *
+ * An ACPI Name must consist of valid ACPI characters. We will repair the name
+ * if necessary because we don't want to abort because of this, but we want
+ * all namespace names to be printable. A warning message is appropriate.
+ *
+ * This issue came up because there are in fact machines that exhibit
+ * this problem, and we want to be able to enable ACPI support for them,
+ * even though there are a few bad names.
+ *
+ ******************************************************************************/
+
+void acpi_ut_repair_name(char *name)
+{
+	u32 i;
+	u8 found_bad_char = FALSE;
+	u32 original_name;
+
+	ACPI_FUNCTION_NAME(ut_repair_name);
+
+	/*
+	 * Special case for the root node. This can happen if we get an
+	 * error during the execution of module-level code.
+	 */
+	if (ACPI_COMPARE_NAMESEG(name, ACPI_ROOT_PATHNAME)) {
+		return;
+	}
+
+	ACPI_COPY_NAMESEG(&original_name, &name[0]);
+
+	/* Check each character in the name */
+
+	for (i = 0; i < ACPI_NAMESEG_SIZE; i++) {
+		if (acpi_ut_valid_name_char(name[i], i)) {
+			continue;
+		}
+
+		/*
+		 * Replace a bad character with something printable, yet technically
+		 * "odd". This prevents any collisions with existing "good"
+		 * names in the namespace.
+		 */
+		name[i] = '_';
+		found_bad_char = TRUE;
+	}
+
+	if (found_bad_char) {
+
+		/* Report warning only if in strict mode or debug mode */
+
+		if (!acpi_gbl_enable_interpreter_slack) {
+			ACPI_WARNING((AE_INFO,
+				      "Invalid character(s) in name (0x%.8X) %p, repaired: [%4.4s]",
+				      original_name, name, &name[0]));
+		} else {
+			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+					  "Invalid character(s) in name (0x%.8X), repaired: [%4.4s]",
+					  original_name, name));
+		}
+	}
+}
+
+#if defined ACPI_ASL_COMPILER || defined ACPI_EXEC_APP
+/*******************************************************************************
+ *
+ * FUNCTION:    ut_convert_backslashes
+ *
+ * PARAMETERS:  pathname        - File pathname string to be converted
+ *
+ * RETURN:      Modifies the input Pathname
+ *
+ * DESCRIPTION: Convert all backslashes (0x5C) to forward slashes (0x2F) within
+ *              the entire input file pathname string.
+ *
+ ******************************************************************************/
+
+void ut_convert_backslashes(char *pathname)
+{
+
+	if (!pathname) {
+		return;
+	}
+
+	while (*pathname) {
+		if (*pathname == '\\') {
+			*pathname = '/';
+		}
+
+		pathname++;
+	}
+}
+#endif