On Thu, Mar 31, 2022 at 11:00:46AM +0200, Greg KH wrote:
> On Thu, Mar 31, 2022 at 08:49:18AM +0000, Won Chung wrote:
> > Component match callback functions need to check if expected data is
> > passed to them. Without this check, it can cause a NULL pointer
> > dereference when another driver registers a component before i915
> > drivers have their component master fully bind.
>
> How can that happen in a real system? Or does this just happen for when
> you are doing development and testing?
>
> >
> > Fixes: 1e8d19d9b0dfc ("mei: hdcp: bind only with i915 on the same PCH")
> > Fixes: c2004ce99ed73 ("mei: pxp: export pavp client to me client bus")
> > Suggested-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > Suggested-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Signed-off-by: Won Chung <wonchung@xxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
>
> Why does this need to go to stable? How can this be triggered in older
> kernels?
>
> > ---
> > Changes from v2:
> > - Correctly add "Suggested-by" tag
> > - Add "Cc: stable@xxxxxxxxxxxxxxx"
> >
> > Changes from v1:
> > - Add "Fixes" tag
> > - Send to stable@xxxxxxxxxxxxxxx
> >
> > 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..843dbc2b21b1 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 (!base || !dev->driver || strcmp(dev->driver->name, "i915") ||
>
> How can base be NULL?
>
>
> > 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..e32a81da8af6 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 (!base || !dev->driver || strcmp(dev->driver->name, "i915") ||
>
> Same here, shouldn't this be caught by the driver core or bus and match
> should not be called?
>
> Why not fix this in the component/driver core instead?
A component is just a device that is declared to be a "component", and
the code that declares it as component does not have to be the driver
of that device. You simply can't assume that it's bind to a driver
like this function does.
In our case the "components" are USB ports, so devices that are never
bind to drivers.
thanks,
--
heikki
