[PATCH 3.2 099/126] net: ep93xx_eth: Do not crash unloading module

Ben Hutchings
2017-02-15T23:03:23Z

From: Florian Fainelli <f.fainelli@gmail.com>

commit c823abac17926767fb50175e098f087a6ac684c3 upstream.

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: 1d22e05df818 ("[PATCH] Cirrus Logic ep93xx ethernet driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/net/ethernet/cirrus/ep93xx_eth.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/drivers/net/ethernet/cirrus/ep93xx_eth.c
+++ b/drivers/net/ethernet/cirrus/ep93xx_eth.c
@@ -469,6 +469,9 @@ static void ep93xx_free_buffers(struct e
struct device *dev = ep->dev->dev.parent;
int i;

+ if (!ep->descs)
+ return;
+
for (i = 0; i < RX_QUEUE_ENTRIES; i++) {
dma_addr_t d;

@@ -493,6 +496,7 @@ static void ep93xx_free_buffers(struct e

dma_free_coherent(dev, sizeof(struct ep93xx_descs), ep->descs,
ep->descs_dma_addr);
+ ep->descs = NULL;
}

static int ep93xx_alloc_buffers(struct ep93xx_priv *ep)