[PATCH] ACPICA: fix NULL pointer dereference in acpi_ns_custom_package()

acpi_ns_custom_package() unconditionally dereferences the first element
of the package to read the _BIX version number, without checking for
NULL:

  if ((*elements)->common.type != ACPI_TYPE_INTEGER)

When firmware returns a _BIX package whose first element is an
unresolvable reference, ACPICA evaluates that entry to NULL.
acpi_ns_remove_null_elements() does not strip NULL entries for
ACPI_PTYPE_CUSTOM packages (fixed-position format would break if
elements were shifted), so acpi_ns_custom_package() sees the NULL
and panics.

 general protection fault, probably for non-canonical address
 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range
 [0x0000000000000008-0x000000000000000f]
 RIP: acpi_ns_check_package
 (drivers/acpi/acpica/nsprepkg.c:634
  drivers/acpi/acpica/nsprepkg.c:110)
 Call Trace:
  <TASK>
  acpi_ns_check_return_value (nspredef.c:136)
  acpi_ns_evaluate (nseval.c:266)
  acpi_evaluate_object (nsxfeval.c:360)
  acpi_battery_get_info (battery.c:537)
  acpi_battery_update (battery.c:1007)
  acpi_battery_add (battery.c:1237)
  acpi_device_probe (bus.c:1076)
  really_probe (dd.c:659)
  </TASK>

Add a NULL check for the first element (version field) before
dereferencing it. The battery probe then fails gracefully with
AE_AML_OPERAND_TYPE instead of crashing the kernel.

Required CONFIG: CONFIG_ACPI_BATTERY=y

Fixes: 7952d40240855932 ("ACPICA: ACPI 6.0: Update _BIX support for new package element")
Reported-by: Xiang Mei <[email protected]>
Signed-off-by: Weiming Shi <[email protected]>
---
 drivers/acpi/acpica/nsprepkg.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/acpi/acpica/nsprepkg.c b/drivers/acpi/acpica/nsprepkg.c
index ca137ce5674f..c32770570120 100644
--- a/drivers/acpi/acpica/nsprepkg.c
+++ b/drivers/acpi/acpica/nsprepkg.c
@@ -631,6 +631,13 @@ acpi_ns_custom_package(struct acpi_evaluate_info *info,
 
 	/* Get version number, must be Integer */
 
+	if (!(*elements)) {
+		ACPI_WARN_PREDEFINED((AE_INFO, info->full_pathname,
+				      info->node_flags,
+				      "Return Package has a NULL version element"));
+		return_ACPI_STATUS(AE_AML_OPERAND_TYPE);
+	}
+
 	if ((*elements)->common.type != ACPI_TYPE_INTEGER) {
 		ACPI_WARN_PREDEFINED((AE_INFO, info->full_pathname,
 				      info->node_flags,
-- 
2.43.0