[PATCH 1/2] misc/mei: Add NULL check to component match callback functions

[Won Chung]

Currently, component_match callback functions used in mei refers to the
driver name, assuming that the component device being matched has a
driver bound. It can cause a NULL pointer dereference when a device
without a driver bound registers a component. This is due to the nature
of the component framework where all registered components are matched
in any component_match callback functions. So even if a component is
registered by a totally irrelevant device, that component is also
shared to these callbacks for i915 driver.

To prevent totally irrelevant device being matched for i915 and causing
a NULL pointer dereference for checking driver name, add a NULL check on
dev->driver to check if there is a driver bound before checking the
driver name.

In the future, the string compare on the driver name, "i915" may need to
be refactored too.

Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Reviewed-by: Prashant Malani <pmalani@xxxxxxxxxxxx>
Signed-off-by: Won Chung <wonchung@xxxxxxxxxx>
---
 drivers/misc/mei/hdcp/mei_hdcp.c | 2 +-
 drivers/misc/mei/pxp/mei_pxp.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
index ec2a4fce8581..e889a8bd7ac8 100644
--- a/drivers/misc/mei/hdcp/mei_hdcp.c
+++ b/drivers/misc/mei/hdcp/mei_hdcp.c
@@ -784,7 +784,7 @@ static int mei_hdcp_component_match(struct device *dev, int subcomponent,
 {
 	struct device *base = data;
 
-	if (strcmp(dev->driver->name, "i915") ||
+	if (!dev->driver || strcmp(dev->driver->name, "i915") ||
 	    subcomponent != I915_COMPONENT_HDCP)
 		return 0;
 
diff --git a/drivers/misc/mei/pxp/mei_pxp.c b/drivers/misc/mei/pxp/mei_pxp.c
index f7380d387bab..5c39457e3f53 100644
--- a/drivers/misc/mei/pxp/mei_pxp.c
+++ b/drivers/misc/mei/pxp/mei_pxp.c
@@ -131,7 +131,7 @@ static int mei_pxp_component_match(struct device *dev, int subcomponent,
 {
 	struct device *base = data;
 
-	if (strcmp(dev->driver->name, "i915") ||
+	if (!dev->driver || strcmp(dev->driver->name, "i915") ||
 	    subcomponent != I915_COMPONENT_PXP)
 		return 0;
 
-- 
2.36.0.rc0.470.gd361397f0d-goog