[PATCH 4.1 21/78] HID: hid-input: Fix accessing freed memory during device disconnect

[Greg Kroah-Hartman]

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>

commit 0621809e37936e7c2b3eac9165cf2aad7f9189eb upstream.

During unbinding the driver was dereferencing a pointer to memory
already freed by power_supply_unregister().

Driver was freeing its internal description of battery through pointers
stored in power_supply structure. However, because the core owns the
power supply instance, after calling power_supply_unregister() this
memory is freed and the driver cannot access these members.

Fix this by storing the pointer to internal description of battery in a
local variable before calling power_supply_unregister(), so the pointer
remains valid.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Reported-by: H.J. Lu <hjl.tools@xxxxxxxxx>
Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/hid/hid-input.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -462,12 +462,15 @@ out:
 
 static void hidinput_cleanup_battery(struct hid_device *dev)
 {
+	const struct power_supply_desc *psy_desc;
+
 	if (!dev->battery)
 		return;
 
+	psy_desc = dev->battery->desc;
 	power_supply_unregister(dev->battery);
-	kfree(dev->battery->desc->name);
-	kfree(dev->battery->desc);
+	kfree(psy_desc->name);
+	kfree(psy_desc);
 	dev->battery = NULL;
 }
 #else  /* !CONFIG_HID_BATTERY_STRENGTH */


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