[PATCH v2 1/1] platform/x86: asus-armoury: fix Use-After-Free and memory leak in driver init

[Marco Scardovi <scardracs@disroot.org>]

In init_rog_tunables(), if dc_limits are defined and allocating
dc_rog_tunables fails, the already allocated ac_rog_tunables gets
freed but the pointer stored in
asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_AC] is not cleared. Since
init_rog_tunables() returns void, the driver initialization continues,
which can lead to a Use-After-Free (UAF) when asus_fw_attr_add()
accesses the freed AC tunables pointer.

Additionally, if init_rog_tunables() succeeds but asus_fw_attr_add()
fails, the allocated tunables are not freed, resulting in a memory leak.

Fix these issues by making init_rog_tunables() return an error code and
propagating it in asus_fw_init(). Defer setting the global pointers in
asus_armoury.rog_tunables until both tunables have been successfully
allocated. If asus_fw_attr_add() fails, release the allocated resources
using a standard goto rollback block in asus_fw_init().

Signed-off-by: Marco Scardovi <scardracs@disroot.org>
---
v2:
- Restructure init_rog_tunables() to use local pointers and defer assignment
  to the global struct until all allocations succeed, eliminating the need
  to set global pointers to NULL on error.
- Use a goto-rollback pattern in asus_fw_init() for cleaner error handling
  as requested by Ilpo.

 drivers/platform/x86/asus-armoury.c | 38 ++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/x86/asus-armoury.c b/drivers/platform/x86/asus-armoury.c
index 495dc1e31d40..ea53a005bb25 100644
--- a/drivers/platform/x86/asus-armoury.c
+++ b/drivers/platform/x86/asus-armoury.c
@@ -989,7 +989,7 @@ static int asus_fw_attr_add(void)
 /* Init / exit ****************************************************************/
 
 /* Set up the min/max and defaults for ROG tunables */
-static void init_rog_tunables(void)
+static int init_rog_tunables(void)
 {
 	const struct power_limits *ac_limits, *dc_limits;
 	struct rog_tunables *ac_rog_tunables = NULL, *dc_rog_tunables = NULL;
@@ -1000,24 +1000,23 @@ static void init_rog_tunables(void)
 	dmi_id = dmi_first_match(power_limits);
 	if (!dmi_id) {
 		pr_warn("No matching power limits found for this system\n");
-		return;
+		return 0;
 	}
 
 	/* Get the power data for this system */
 	power_data = dmi_id->driver_data;
 	if (!power_data) {
 		pr_info("No power data available for this system\n");
-		return;
+		return 0;
 	}
 
 	/* Initialize AC power tunables */
 	ac_limits = power_data->ac_data;
 	if (ac_limits) {
-		ac_rog_tunables = kzalloc_obj(*asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_AC]);
+		ac_rog_tunables = kzalloc_obj(*ac_rog_tunables);
 		if (!ac_rog_tunables)
-			goto err_nomem;
+			return -ENOMEM;
 
-		asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_AC] = ac_rog_tunables;
 		ac_rog_tunables->power_limits = ac_limits;
 
 		/* Set initial AC values */
@@ -1060,13 +1059,12 @@ static void init_rog_tunables(void)
 	/* Initialize DC power tunables */
 	dc_limits = power_data->dc_data;
 	if (dc_limits) {
-		dc_rog_tunables = kzalloc_obj(*asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_DC]);
+		dc_rog_tunables = kzalloc_obj(*dc_rog_tunables);
 		if (!dc_rog_tunables) {
 			kfree(ac_rog_tunables);
-			goto err_nomem;
+			return -ENOMEM;
 		}
 
-		asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_DC] = dc_rog_tunables;
 		dc_rog_tunables->power_limits = dc_limits;
 
 		/* Set initial DC values */
@@ -1106,15 +1104,16 @@ static void init_rog_tunables(void)
 		pr_debug("No DC PPT limits defined\n");
 	}
 
-	return;
+	asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_AC] = ac_rog_tunables;
+	asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_DC] = dc_rog_tunables;
 
-err_nomem:
-	pr_err("Failed to allocate memory for tunables\n");
+	return 0;
 }
 
 static int __init asus_fw_init(void)
 {
 	char *wmi_uid;
+	int err;
 
 	wmi_uid = wmi_get_acpi_device_uid(ASUS_WMI_MGMT_GUID);
 	if (!wmi_uid)
@@ -1127,10 +1126,21 @@ static int __init asus_fw_init(void)
 	if (!strcmp(wmi_uid, ASUS_ACPI_UID_ASUSWMI))
 		return -ENODEV;
 
-	init_rog_tunables();
+	err = init_rog_tunables();
+	if (err)
+		return err;
 
 	/* Must always be last step to ensure data is available */
-	return asus_fw_attr_add();
+	err = asus_fw_attr_add();
+	if (err)
+		goto err_free_tunables;
+
+	return 0;
+
+err_free_tunables:
+	kfree(asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_AC]);
+	kfree(asus_armoury.rog_tunables[ASUS_ROG_TUNABLE_DC]);
+	return err;
 }
 
 static void __exit asus_fw_exit(void)
-- 
2.55.0