[PATCH 4.4 047/138] remoteproc: Fix potential race condition in rproc_add

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

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

From: Dave Gerlach <redacted>

commit d2e12e66a939c54ed84e5f1b6947f0c45f6c56eb upstream.

rproc_add adds the newly created remoteproc to a list for use by
rproc_get_by_phandle and then does some additional processing to finish
adding the remoteproc. This leaves a small window of time in which the
rproc is available in the list but not yet fully initialized, so if
another driver comes along and gets a handle to the rproc, it will be
invalid. Rearrange the code in rproc_add to make sure the rproc is added
to the list only after it has been successfuly initialized.

Fixes: fec47d863587 ("remoteproc: introduce rproc_get_by_phandle API")
Signed-off-by: Dave Gerlach <redacted>
Signed-off-by: Bjorn Andersson <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/remoteproc/remoteproc_core.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c

@@ -1239,11 +1239,6 @@ int rproc_add(struct rproc *rproc)
 	if (ret < 0)
 		return ret;
 
-	/* expose to rproc_get_by_phandle users */
-	mutex_lock(&rproc_list_mutex);
-	list_add(&rproc->node, &rproc_list);
-	mutex_unlock(&rproc_list_mutex);
-
 	dev_info(dev, "%s is available\n", rproc->name);
 
 	dev_info(dev, "Note: remoteproc is still under development and considered experimental.\n");

@@ -1251,8 +1246,16 @@ int rproc_add(struct rproc *rproc)
 
 	/* create debugfs entries */
 	rproc_create_debug_dir(rproc);
+	ret = rproc_add_virtio_devices(rproc);
+	if (ret < 0)
+		return ret;
+
+	/* expose to rproc_get_by_phandle users */
+	mutex_lock(&rproc_list_mutex);
+	list_add(&rproc->node, &rproc_list);
+	mutex_unlock(&rproc_list_mutex);
 
-	return rproc_add_virtio_devices(rproc);
+	return 0;
 }
 EXPORT_SYMBOL(rproc_add);