[PATCH v4] remoteproc: Fix NULL pointer dereference in rproc_virtio_notify

[Nikita Shubin]

Undefined rproc_ops .kick method in remoteproc driver will result in
"Unable to handle kernel NULL pointer dereference" in rproc_virtio_notify, 
after firmware loading if:

 1) .kick method wasn't defined in driver
 2) resource_table exists in firmware and has "Virtio device entry" defined

Let's refuse to register an rproc-induced virtio device if no kick method was
defined for rproc.

Signed-off-by: Nikita Shubin <NShubin@xxxxxxxxxx>
Fixes: 7a186941626d ("remoteproc: remove the single rpmsg vdev limitation")
Cc: stable@xxxxxxxxxxxxxxx
---
 drivers/remoteproc/remoteproc_virtio.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
index 8c07cb2ca8ba..31a62a0b470e 100644
--- a/drivers/remoteproc/remoteproc_virtio.c
+++ b/drivers/remoteproc/remoteproc_virtio.c
@@ -334,6 +334,13 @@ int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
 	struct rproc_mem_entry *mem;
 	int ret;
 
+	if (rproc->ops->kick == NULL) {
+		ret = -EINVAL;
+		dev_err(dev, ".kick method not defined for %s",
+				rproc->name);
+		goto out;
+	}
+
 	/* Try to find dedicated vdev buffer carveout */
 	mem = rproc_find_carveout_by_name(rproc, "vdev%dbuffer", rvdev->index);
 	if (mem) {
-- 
2.24.1