[char-misc-next] mei: fix double freeing of a cb during link reset

[Tomas Winkler]

From: Alexander Usyskin <alexander.usyskin@xxxxxxxxx>

Fix double freeing of the cb that can happen if link reset kicks  in the
middle of blocked write from a device on the cl bus.

Free cb inside mei_cl_write function on failure and drop cb free
operation from callers, during a link reset the mei_cl_write function
returns with an error,  but the caller doesn't know if the cb was
already queued or not so it doesn't know if the cb will be freed upon
queue reclaim or it has to free it itself.

Signed-off-by: Alexander Usyskin <alexander.usyskin@xxxxxxxxx>
Signed-off-by: Tomas Winkler <tomas.winkler@xxxxxxxxx>
---
 drivers/misc/mei/bus.c    |  4 +---
 drivers/misc/mei/client.c |  4 +++-
 drivers/misc/mei/main.c   | 26 ++++++++++----------------
 3 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index f4cf43b47c7a..5d5996e39a67 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -44,7 +44,7 @@ ssize_t __mei_cl_send(struct mei_cl *cl, u8 *buf, size_t length,
 			bool blocking)
 {
 	struct mei_device *bus;
-	struct mei_cl_cb *cb = NULL;
+	struct mei_cl_cb *cb;
 	ssize_t rets;
 
 	if (WARN_ON(!cl || !cl->dev))
@@ -86,8 +86,6 @@ ssize_t __mei_cl_send(struct mei_cl *cl, u8 *buf, size_t length,
 
 out:
 	mutex_unlock(&bus->device_lock);
-	if (rets < 0)
-		mei_io_cb_free(cb);
 
 	return rets;
 }
diff --git a/drivers/misc/mei/client.c b/drivers/misc/mei/client.c
index af6816bc268f..a9cdb92b52d1 100644
--- a/drivers/misc/mei/client.c
+++ b/drivers/misc/mei/client.c
@@ -1645,7 +1645,7 @@ int mei_cl_write(struct mei_cl *cl, struct mei_cl_cb *cb, bool blocking)
 	if (rets < 0 && rets != -EINPROGRESS) {
 		pm_runtime_put_noidle(dev->dev);
 		cl_err(dev, cl, "rpm: get failed %d\n", rets);
-		return rets;
+		goto free;
 	}
 
 	cb->buf_idx = 0;
@@ -1724,6 +1724,8 @@ err:
 	cl_dbg(dev, cl, "rpm: autosuspend\n");
 	pm_runtime_mark_last_busy(dev->dev);
 	pm_runtime_put_autosuspend(dev->dev);
+free:
+	mei_io_cb_free(cb);
 
 	return rets;
 }
diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 17970163eacc..05775a6f7c88 100644
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -267,7 +267,7 @@ static ssize_t mei_write(struct file *file, const char __user *ubuf,
 			 size_t length, loff_t *offset)
 {
 	struct mei_cl *cl = file->private_data;
-	struct mei_cl_cb *write_cb = NULL;
+	struct mei_cl_cb *cb;
 	struct mei_device *dev;
 	int rets;
 
@@ -305,36 +305,30 @@ static ssize_t mei_write(struct file *file, const char __user *ubuf,
 	}
 
 	*offset = 0;
-	write_cb = mei_cl_alloc_cb(cl, length, MEI_FOP_WRITE, file);
-	if (!write_cb) {
+	cb = mei_cl_alloc_cb(cl, length, MEI_FOP_WRITE, file);
+	if (!cb) {
 		rets = -ENOMEM;
 		goto out;
 	}
 
-	rets = copy_from_user(write_cb->buf.data, ubuf, length);
+	rets = copy_from_user(cb->buf.data, ubuf, length);
 	if (rets) {
 		dev_dbg(dev->dev, "failed to copy data from userland\n");
 		rets = -EFAULT;
+		mei_io_cb_free(cb);
 		goto out;
 	}
 
 	if (cl == &dev->iamthif_cl) {
-		rets = mei_amthif_write(cl, write_cb);
-
-		if (rets) {
-			dev_err(dev->dev,
-				"amthif write failed with status = %d\n", rets);
-			goto out;
-		}
-		mutex_unlock(&dev->device_lock);
-		return length;
+		rets = mei_amthif_write(cl, cb);
+		if (!rets)
+			rets = length;
+		goto out;
 	}
 
-	rets = mei_cl_write(cl, write_cb, false);
+	rets = mei_cl_write(cl, cb, false);
 out:
 	mutex_unlock(&dev->device_lock);
-	if (rets < 0)
-		mei_io_cb_free(write_cb);
 	return rets;
 }
 
-- 
2.4.3