[char-misc-next 0/3] mei: bus: null derefence in rx

[char-misc-next 0/3] mei: bus: null derefence in rx

[Tomas Winkler]

Fix race in receive callback for drivers on me client
bus, that results in null dereferencing and improve 
the error handling.
The first patch 'mei: protect mei_cl_mtu from null dereference'
itself is sufficient to prevent the failure and is intended
for stable.


Alexander Usyskin (3):
  mei: protect mei_cl_mtu from null dereference
  mei: bus: do not start a read for disconnected clients
  mei: bus: deinitialize callback functions on init failure

 drivers/misc/mei/bus.c    | 18 ++++++++++++++----
 drivers/misc/mei/client.h |  4 ++--
 2 files changed, 16 insertions(+), 6 deletions(-)

-- 
2.25.4

[char-misc-next 1/3] mei: protect mei_cl_mtu from null dereference

[Tomas Winkler]

From: Alexander Usyskin <alexander.usyskin@intel.com>

A receive callback is queued while the client is still connected
but can still be called after the client was disconnected. Upon
disconnect cl->me_cl is set to NULL, hence we need to check
that ME client is not-NULL in mei_cl_mtu to avoid
null dereference.

Cc: <stable@vger.kernel.org>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
 drivers/misc/mei/client.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/client.h b/drivers/misc/mei/client.h
index 64143d4ec758..9e08a9843bba 100644
--- a/drivers/misc/mei/client.h
+++ b/drivers/misc/mei/client.h
@@ -182,11 +182,11 @@ static inline u8 mei_cl_me_id(const struct mei_cl *cl)
  *
  * @cl: host client
  *
- * Return: mtu
+ * Return: mtu or 0 if client is not connected
  */
 static inline size_t mei_cl_mtu(const struct mei_cl *cl)
 {
-	return cl->me_cl->props.max_msg_length;
+	return cl->me_cl ? cl->me_cl->props.max_msg_length : 0;
 }
 
 /**
-- 
2.25.4

[char-misc-next 2/3] mei: bus: do not start a read for disconnected clients

[Tomas Winkler]

From: Alexander Usyskin <alexander.usyskin@intel.com>

Avoid queuing reads and registering rx callbacks in
case the client is not connected, to prevent null
dereferencing and memory leaks.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
 drivers/misc/mei/bus.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 9cdaa7f3af23..1a54bf3ed0c3 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -276,7 +276,8 @@ static void mei_cl_bus_rx_work(struct work_struct *work)
 		cldev->rx_cb(cldev);
 
 	mutex_lock(&bus->device_lock);
-	mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	if (mei_cl_is_connected(cldev->cl))
+		mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
 	mutex_unlock(&bus->device_lock);
 }
 
@@ -364,7 +365,10 @@ int mei_cldev_register_rx_cb(struct mei_cl_device *cldev, mei_cldev_cb_t rx_cb)
 	INIT_WORK(&cldev->rx_work, mei_cl_bus_rx_work);
 
 	mutex_lock(&bus->device_lock);
-	ret = mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	if (mei_cl_is_connected(cldev->cl))
+		ret = mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	else
+		ret = -ENODEV;
 	mutex_unlock(&bus->device_lock);
 	if (ret && ret != -EBUSY)
 		return ret;
-- 
2.25.4

[char-misc-next 3/3] mei: bus: deinitialize callback functions on init failure

[Tomas Winkler]

From: Alexander Usyskin <alexander.usyskin@intel.com>

If the initialization procedure for receive or receive callback
registration on the client bus has failed the caller can't re-run it.
Deinitilize the callback pointers and cancel the work
to allow the caller to retry.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
 drivers/misc/mei/bus.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 1a54bf3ed0c3..76aa0e93748a 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -370,8 +370,11 @@ int mei_cldev_register_rx_cb(struct mei_cl_device *cldev, mei_cldev_cb_t rx_cb)
 	else
 		ret = -ENODEV;
 	mutex_unlock(&bus->device_lock);
-	if (ret && ret != -EBUSY)
+	if (ret && ret != -EBUSY) {
+		cancel_work_sync(&cldev->rx_work);
+		cldev->rx_cb = NULL;
 		return ret;
+	}
 
 	return 0;
 }
@@ -405,8 +408,11 @@ int mei_cldev_register_notif_cb(struct mei_cl_device *cldev,
 	mutex_lock(&bus->device_lock);
 	ret = mei_cl_notify_request(cldev->cl, NULL, 1);
 	mutex_unlock(&bus->device_lock);
-	if (ret)
+	if (ret) {
+		cancel_work_sync(&cldev->notif_work);
+		cldev->notif_cb = NULL;
 		return ret;
+	}
 
 	return 0;
 }
-- 
2.25.4