dmatest: Fix NULL pointer dereference on ioat

device_control is an optional and not implemented in all DMA drivers.
Any calls to these will result in a NULL pointer dereference.  dmatest
makes two of these calls when completing the kernel thread and removing
the module.  These are corrected by calling the dmaengine_device_control
wrapper and checking for a non-existant device_control function pointer
there.

Signed-off-by: Jon Mason <jon.mason@intel.com>
CC: Vinod Koul <vinod.koul@intel.com>
CC: Dan Williams <djbw@fb.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 3aa76dbed166..be6e95395b11 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -608,7 +608,10 @@ static inline int dmaengine_device_control(struct dma_chan *chan,
                                            enum dma_ctrl_cmd cmd,
                                            unsigned long arg)
 {
-        return chan->device->device_control(chan, cmd, arg);
+        if (chan->device->device_control)
+                return chan->device->device_control(chan, cmd, arg);
+        else
+                return -ENOSYS;
 }
 
 static inline int dmaengine_slave_config(struct dma_chan *chan,