linux-kernel - [PATCH 4.9 54/64] platform/x86: alienware-wmi: fix kfree on potentially uninitialized pointer

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Date:   Tue, 26 May 2020 20:53:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        "Darren Hart (VMware)" <dvhart@...radead.org>
Subject: [PATCH 4.9 54/64] platform/x86: alienware-wmi: fix kfree on potentially uninitialized pointer

From: Colin Ian King <colin.king@...onical.com>

commit 98e2630284ab741804bd0713e932e725466f2f84 upstream.

Currently the kfree of output.pointer can be potentially freeing
an uninitalized pointer in the case where out_data is NULL. Fix this
by reworking the case where out_data is not-null to perform the
ACPI status check and also the kfree of outpoint.pointer in one block
and hence ensuring the pointer is only freed when it has been used.

Also replace the if (ptr != NULL) idiom with just if (ptr).

Fixes: ff0e9f26288d ("platform/x86: alienware-wmi: Correct a memory leak")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: Darren Hart (VMware) <dvhart@...radead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/platform/x86/alienware-wmi.c |   17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

--- a/drivers/platform/x86/alienware-wmi.c
+++ b/drivers/platform/x86/alienware-wmi.c
@@ -504,23 +504,22 @@ static acpi_status alienware_wmax_comman
 
 	input.length = (acpi_size) sizeof(*in_args);
 	input.pointer = in_args;
-	if (out_data != NULL) {
+	if (out_data) {
 		output.length = ACPI_ALLOCATE_BUFFER;
 		output.pointer = NULL;
 		status = wmi_evaluate_method(WMAX_CONTROL_GUID, 1,
 					     command, &input, &output);
-	} else
+		if (ACPI_SUCCESS(status)) {
+			obj = (union acpi_object *)output.pointer;
+			if (obj && obj->type == ACPI_TYPE_INTEGER)
+				*out_data = (u32)obj->integer.value;
+		}
+		kfree(output.pointer);
+	} else {
 		status = wmi_evaluate_method(WMAX_CONTROL_GUID, 1,
 					     command, &input, NULL);
-
-	if (ACPI_SUCCESS(status) && out_data != NULL) {
-		obj = (union acpi_object *)output.pointer;
-		if (obj && obj->type == ACPI_TYPE_INTEGER)
-			*out_data = (u32) obj->integer.value;
 	}
-	kfree(output.pointer);
 	return status;
-
 }
 
 /*