dmatest: fix use after free in dmatest_exit

dmatest_cleanup_chanel will free dtc, so grab ->chan before it goes away
and use it to do the release.

Reported-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index 732fa1ec36ab..e190d8b30700 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -430,13 +430,15 @@ late_initcall(dmatest_init);
 static void __exit dmatest_exit(void)
 {
         struct dmatest_chan *dtc, *_dtc;
+        struct dma_chan *chan;
 
         list_for_each_entry_safe(dtc, _dtc, &dmatest_channels, node) {
                 list_del(&dtc->node);
+                chan = dtc->chan;
                 dmatest_cleanup_channel(dtc);
                 pr_debug("dmatest: dropped channel %s\n",
-                         dma_chan_name(dtc->chan));
-                dma_release_channel(dtc->chan);
+                         dma_chan_name(chan));
+                dma_release_channel(chan);
         }
 }
 module_exit(dmatest_exit);