ACPI / bus: Do not traverse through non-existed device table

Would the following work for you?

--- 8< --- 8< --- 8< ---
From 03013c0c1e487cda4c0d8dc5065ed2f0031095de Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <[email protected]>
Date: Thu, 1 Feb 2018 21:52:14 +0200
Subject: [PATCH 1/1] ACPI / bus: Do not traverse through non-existed device
table

When __acpi_match_device() is called it would be possible to have ACPI ID table a MULL pointer. To avoid potential dereference, check for this before traverse.

This patch implies a bit of refactoring acpi_of_match_device() to return pointer to OF ID when matched followed by refactoring __acpi_match_device() to return either ACPI or OF ID when matches.

While here, remove redundant 'else'.

---
 drivers/acpi/bus.c | 66 +++++++++++++++++++++++++++++++++------------
---------
 1 file changed, 41 insertions(+), 25 deletions(-)

+ const struct of_device_id
*of_match_table,
+ const struct of_device_id **of_id)
{
const union acpi_object *of_compatible, *obj;
int i, nval;
@@ -690,8 +692,11 @@ static bool acpi_of_match_device(struct acpi_device *adev,
const struct of_device_id *id;

for (id = of_match_table; id->compatible[0]; id++)
- if (!strcasecmp(obj->string.pointer, id-

+ if (!strcasecmp(obj->string.pointer, id-

+ if (of_id)
+ *of_id = id;
return true;
+ }
}

return false;
@@ -762,10 +767,11 @@ static bool __acpi_match_device_cls(const struct acpi_device_id *id,
return true;
}

-static const struct acpi_device_id *__acpi_match_device(
- struct acpi_device *device,
- const struct acpi_device_id *ids,
- const struct of_device_id *of_ids)
+static bool __acpi_match_device(struct acpi_device *device,
+ const struct acpi_device_id *acpi_ids,
+ const struct of_device_id *of_ids,
+ const struct acpi_device_id **acpi_id,
+ const struct of_device_id **of_id)
{
const struct acpi_device_id *id;
struct acpi_hardware_id *hwid;
@@ -775,30 +781,35 @@ static const struct acpi_device_id *__acpi_match_device(
* driver for it.
*/
if (!device || !device->status.present)
- return NULL;
+ return false;

list_for_each_entry(hwid, &device->pnp.ids, list) {
/* First, check the ACPI/PNP IDs provided by the
caller. */
- for (id = ids; id->id[0] || id->cls; id++) {
- if (id->id[0] && !strcmp((char *) id->id, hwid-

- return id;
- else if (id->cls && __acpi_match_device_cls(id,
hwid))
- return id;
+ if (acpi_ids) {
+ bool found;
+
+ for (id = acpi_ids; id->id[0] || id->cls; id++)
{
+ found = false;
+ if (id->id[0] && !strcmp((char *)id-

+ found = true;
+ if (id->cls &&
__acpi_match_device_cls(id, hwid))
+ found = true;
+ if (found) {
+ if (acpi_id)
+ *acpi_id = id;
+ return true;
+ }
+ }
}

/*
* Next, check ACPI_DT_NAMESPACE_HID and try to match
the
* "compatible" property if found.
- *
- * The id returned by the below is not valid, but the
only
- * caller passing non-NULL of_ids here is only
interested in
- * whether or not the return value is NULL.
*/
- if (!strcmp(ACPI_DT_NAMESPACE_HID, hwid->id)
- && acpi_of_match_device(device, of_ids))
- return id;
+ if (!strcmp(ACPI_DT_NAMESPACE_HID, hwid->id))
+ return acpi_of_match_device(device, of_ids,
of_id);
}
- return NULL;
+ return false;
}

/**
@@ -815,7 +826,10 @@ static const struct acpi_device_id *__acpi_match_device(
const struct acpi_device_id *acpi_match_device(const struct
acpi_device_id *ids,
const struct device
*dev)
{
- return __acpi_match_device(acpi_companion_match(dev), ids,
NULL);
+ const struct acpi_device_id *id = NULL;
+
+ __acpi_match_device(acpi_companion_match(dev), ids, NULL, &id,
NULL);
+ return id;
}
EXPORT_SYMBOL_GPL(acpi_match_device);

@@ -840,7 +854,7 @@ EXPORT_SYMBOL_GPL(acpi_get_match_data);
int acpi_match_device_ids(struct acpi_device *device,
const struct acpi_device_id *ids)
{
- return __acpi_match_device(device, ids, NULL) ? 0 : -ENOENT;
+ return __acpi_match_device(device, ids, NULL, NULL, NULL) ? 0 :
-ENOENT;
}
EXPORT_SYMBOL(acpi_match_device_ids);

@@ -849,10 +863,12 @@ bool acpi_driver_match_device(struct device *dev,
{
if (!drv->acpi_match_table)
return acpi_of_match_device(ACPI_COMPANION(dev),

-					    drv->of_match_table);
+					    drv->of_match_table,
+					    NULL);

- return !!__acpi_match_device(acpi_companion_match(dev),
- drv->acpi_match_table, drv-

+ return __acpi_match_device(acpi_companion_match(dev),
+ drv->acpi_match_table, drv-

+ NULL, NULL);
}
EXPORT_SYMBOL_GPL(acpi_driver_match_device);

index 676c9788e1c8..33c5166e6028 100644
@@ -660,13 +660,15 @@ struct acpi_device *acpi_companion_match(const

struct device *dev)
* acpi_of_match_device - Match device object using the "compatible"
property.
* @adev: ACPI device object to match.
* @of_match_table: List of device IDs to match against.
+ * @of_id: OF ID if matched
*
* If @dev has an ACPI companion which has ACPI_DT_NAMESPACE_HID in its
list of
* identifiers and a _DSD object with the "compatible" property, use
that
* property to match against the given list of identifiers. */
static bool acpi_of_match_device(struct acpi_device *adev,
- const struct of_device_id
*of_match_table)