linux-kernel - [PATCH] Revert "ACPICA: Interpreter: fix memory leak by using existing buffer"

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Date:   Sat,  6 Feb 2021 09:49:37 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        devel@...ica.org, Ard Biesheuvel <ardb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Kaneda <erik.kaneda@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>, Shawn Guo <shawn.guo@...aro.org>
Subject: [PATCH] Revert "ACPICA: Interpreter: fix memory leak by using existing buffer"

This reverts commit 32cf1a12cad43358e47dac8014379c2f33dfbed4.

The 'exisitng buffer' in this case is the firmware provided table, and
we should not modify that in place. This fixes a crash on arm64 with
initrd table overrides, in which case the DSDT is not mapped with
read/write permissions.

Cc: Robert Moore <robert.moore@...el.com>
Cc: Erik Kaneda <erik.kaneda@...el.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Cc: Len Brown <lenb@...nel.org>
Reported-by: Shawn Guo <shawn.guo@...aro.org>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 drivers/acpi/acpica/nsrepair2.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/acpica/nsrepair2.c b/drivers/acpi/acpica/nsrepair2.c
index d2c8d8279e7a..24c197d91f29 100644
--- a/drivers/acpi/acpica/nsrepair2.c
+++ b/drivers/acpi/acpica/nsrepair2.c
@@ -495,8 +495,9 @@ acpi_ns_repair_HID(struct acpi_evaluate_info *info,
 		   union acpi_operand_object **return_object_ptr)
 {
 	union acpi_operand_object *return_object = *return_object_ptr;
-	char *dest;
+	union acpi_operand_object *new_string;
 	char *source;
+	char *dest;
 
 	ACPI_FUNCTION_NAME(ns_repair_HID);
 
@@ -517,6 +518,13 @@ acpi_ns_repair_HID(struct acpi_evaluate_info *info,
 		return_ACPI_STATUS(AE_OK);
 	}
 
+	/* It is simplest to always create a new string object */
+
+	new_string = acpi_ut_create_string_object(return_object->string.length);
+	if (!new_string) {
+		return_ACPI_STATUS(AE_NO_MEMORY);
+	}
+
 	/*
 	 * Remove a leading asterisk if present. For some unknown reason, there
 	 * are many machines in the field that contains IDs like this.
@@ -526,7 +534,7 @@ acpi_ns_repair_HID(struct acpi_evaluate_info *info,
 	source = return_object->string.pointer;
 	if (*source == '*') {
 		source++;
-		return_object->string.length--;
+		new_string->string.length--;
 
 		ACPI_DEBUG_PRINT((ACPI_DB_REPAIR,
 				  "%s: Removed invalid leading asterisk\n",
@@ -541,11 +549,12 @@ acpi_ns_repair_HID(struct acpi_evaluate_info *info,
 	 * "NNNN####" where N is an uppercase letter or decimal digit, and
 	 * # is a hex digit.
 	 */
-	for (dest = return_object->string.pointer; *source; dest++, source++) {
+	for (dest = new_string->string.pointer; *source; dest++, source++) {
 		*dest = (char)toupper((int)*source);
 	}
-	return_object->string.pointer[return_object->string.length] = 0;
 
+	acpi_ut_remove_reference(return_object);
+	*return_object_ptr = new_string;
 	return_ACPI_STATUS(AE_OK);
 }
 
-- 
2.30.0