When we unload the ep93xx_eth, whether we have opened the network
interface or not, we will either hit a kernel paging request error, or a
simple NULL pointer de-reference because:
- if ep93xx_open has been called, we have created a valid DMA mapping
for ep->descs, when we call ep93xx_stop, we also call
ep93xx_free_buffers, ep->descs now has a stale value
- if ep93xx_open has not been called, we have a NULL pointer for
ep->descs, so performing any operation against that address just won't
work
Fix this by adding a NULL pointer check for ep->descs which means that
ep93xx_free_buffers() was able to successfully tear down the descriptors
and free the DMA cookie as well.
Fixes: 1d22e05df8 ("[PATCH] Cirrus Logic ep93xx ethernet driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
c823abac17