linux-kernel - [char-misc-next 2/3] mei: fix NULL dereferencing during FW initiated disconnection

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Date:	Sun, 17 Apr 2016 12:16:03 -0400
From:	Tomas Winkler <tomas.winkler@...el.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Alexander Usyskin <alexander.usyskin@...el.com>,
	linux-kernel@...r.kernel.org, <stable@...r.kernel.org>,
	Tomas Winkler <tomas.winkler@...el.com>
Subject: [char-misc-next 2/3] mei: fix NULL dereferencing during FW initiated disconnection

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

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.

Cc: <stable@...r.kernel.org> #4.2+
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.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 bab17e4197b6..09f5280fa021 100644
--- a/drivers/misc/mei/client.c
+++ b/drivers/misc/mei/client.c
@@ -1767,6 +1767,10 @@ 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 5eaa4638e824..5aa606c8a827 100644
--- a/drivers/misc/mei/hbm.c
+++ b/drivers/misc/mei/hbm.c
@@ -877,8 +877,7 @@ 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 1e5cb1f704f8..704dc6caad6d 100644
--- a/drivers/misc/mei/interrupt.c
+++ b/drivers/misc/mei/interrupt.c
@@ -194,10 +194,7 @@ 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;
 }
-- 
2.5.5