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net: ep93xx_eth: Do not crash unloading module

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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>
This commit is contained in:
Florian Fainelli 2016-12-04 19:22:05 -08:00 committed by David S. Miller
parent 34e0f2c2d8
commit c823abac17
1 changed files with 4 additions and 0 deletions
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4
drivers/net/ethernet/cirrus/ep93xx_eth.c
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@ -468,6 +468,9 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
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;
@ -490,6 +493,7 @@ static void ep93xx_free_buffers(struct ep93xx_priv *ep)
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)