[PATCH 4.2.y-ckt 047/206] mei: fix NULL dereferencing during FW initiated disconnection

[Kamal Mostafa]

4.2.8-ckt12 -stable review patch.  If anyone has any objections, please let me 
know.

---8<------------------------------------------------------------

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

commit 6a8d648c8d1824117a9e9edb948ed1611fb013c0 upstream.

In the case when disconnection is initiated from the FW
the driver is flushing items from the write control list while
iterating over it:

mei_irq_write_handler()
    list_for_each_entry_safe(ctrl_wr_list)         <-- outer loop
         mei_cl_irq_disconnect_rsp()
             mei_cl_set_disconnected()
                 mei_io_list_flush(ctrl_wr_list)   <-- destorying list

We move the list flushing to the completion routine.

Signed-off-by: Alexander Usyskin <alexander.usys...@intel.com>
Signed-off-by: Tomas Winkler <tomas.wink...@intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
 drivers/misc/mei/client.c    | 4 ++++
 drivers/misc/mei/hbm.c       | 3 +--
 drivers/misc/mei/interrupt.c | 5 +----
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/misc/mei/client.c b/drivers/misc/mei/client.c
index 6decbe1..b364117 100644
--- a/drivers/misc/mei/client.c
+++ b/drivers/misc/mei/client.c
@@ -1490,6 +1490,10 @@ void mei_cl_complete(struct mei_cl *cl, struct mei_cl_cb 
*cb)
                        wake_up(&cl->wait);
 
                break;
+       case MEI_FOP_DISCONNECT_RSP:
+               mei_io_cb_free(cb);
+               mei_cl_set_disconnected(cl);
+               break;
        default:
                BUG_ON(0);
        }
diff --git a/drivers/misc/mei/hbm.c b/drivers/misc/mei/hbm.c
index a4f2831..070c9bc 100644
--- a/drivers/misc/mei/hbm.c
+++ b/drivers/misc/mei/hbm.c
@@ -687,8 +687,7 @@ static int mei_hbm_fw_disconnect_req(struct mei_device *dev,
                cb = mei_io_cb_init(cl, MEI_FOP_DISCONNECT_RSP, NULL);
                if (!cb)
                        return -ENOMEM;
-               cl_dbg(dev, cl, "add disconnect response as first\n");
-               list_add(&cb->list, &dev->ctrl_wr_list.list);
+               list_add_tail(&cb->list, &dev->ctrl_wr_list.list);
        }
        return 0;
 }
diff --git a/drivers/misc/mei/interrupt.c b/drivers/misc/mei/interrupt.c
index 3f34052..15dbac8 100644
--- a/drivers/misc/mei/interrupt.c
+++ b/drivers/misc/mei/interrupt.c
@@ -180,10 +180,7 @@ static int mei_cl_irq_disconnect_rsp(struct mei_cl *cl, 
struct mei_cl_cb *cb,
                return -EMSGSIZE;
 
        ret = mei_hbm_cl_disconnect_rsp(dev, cl);
-       mei_cl_set_disconnected(cl);
-       mei_io_cb_free(cb);
-       mei_me_cl_put(cl->me_cl);
-       cl->me_cl = NULL;
+       list_move_tail(&cb->list, &cmpl_list->list);
 
        return ret;
 }
-- 
2.7.4