linux-kernel - [PATCH 1/2] ACPI: Fix stale pointer access to flags.lockable

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Date:	Mon, 15 Oct 2012 10:34:29 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	linux-acpi@...r.kernel.org, lenb@...nel.org
Cc:	linux-kernel@...r.kernel.org, rjw@...k.pl,
	isimatu.yasuaki@...fujitsu.com, liuj97@...il.com,
	Toshi Kani <toshi.kani@...com>
Subject: [PATCH 1/2] ACPI: Fix stale pointer access to flags.lockable

During hot-remove, acpi_bus_hot_remove_device() calls ACPI _LCK
method when device->flags.lockable is set. However, this device
pointer is stale since the target acpi_device object has been
already kfree'd by acpi_bus_trim().

The flags.lockable indicates whether or not this ACPI object
implements _LCK method. Fix the stable pointer access by replacing
it with acpi_get_handle() to check if _LCK is implemented.

Signed-off-by: Toshi Kani <toshi.kani@...com>
---
 drivers/acpi/scan.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 1fcb867..ed87f43 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -97,6 +97,7 @@ void acpi_bus_hot_remove_device(void *context)
 	struct acpi_eject_event *ej_event = (struct acpi_eject_event *) context;
 	struct acpi_device *device;
 	acpi_handle handle = ej_event->handle;
+	acpi_handle temp;
 	struct acpi_object_list arg_list;
 	union acpi_object arg;
 	acpi_status status = AE_OK;
@@ -117,13 +118,16 @@ void acpi_bus_hot_remove_device(void *context)
 		goto err_out;
 	}
 
+	/* device has been freed */
+	device = NULL;
+
 	/* power off device */
 	status = acpi_evaluate_object(handle, "_PS3", NULL, NULL);
 	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND)
 		printk(KERN_WARNING PREFIX
 				"Power-off device failed\n");
 
-	if (device->flags.lockable) {
+	if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &temp))) {
 		arg_list.count = 1;
 		arg_list.pointer = &arg;
 		arg.type = ACPI_TYPE_INTEGER;
-- 
1.7.11.7

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