[netdevice] Do not attempt to unmap a null I/O buffer

netdev_tx_err() may be called with a null I/O buffer (e.g. to record a
transmit error with no associated buffer).  Avoid a potential null
pointer dereference in the DMA unmapping code path.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/net/netdevice.c b/src/net/netdevice.c
index f3feca26bfed7956788b811f3b104dff524e73a3..754799cd1da37f13fc4a15b863690b435332629f 100644 (file)
--- a/src/net/netdevice.c
+++ b/src/net/netdevice.c
@@ -392,7 +392,7 @@ void netdev_tx_err ( struct net_device *netdev,
        }
 
        /* Unmap I/O buffer, if required */
-       if ( dma_mapped ( &iobuf->map ) )
+       if ( iobuf && dma_mapped ( &iobuf->map ) )
                iob_unmap ( iobuf );
 
        /* Discard packet */