[PATCH] PCI: endpoint: pci-epf-test: NULL check dma channels before release

["Shin'ichiro Kawasaki" <shinichiro.kawasaki@xxxxxxx>]

When endpoint controller driver is immature, the fields dma_chan_tx and
dma_chan_rx of the struct pci_epf_test could be NULL even after epf
initialization. However, pci_epf_test_clean_dma_chan() assumes that they
are always non-NULL valid values, and causes kernel panic when the
fields are NULL. To avoid the kernel panic, NULL check the fields before
release.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index e091193bd8a8..1c29d5dd4382 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -301,15 +301,20 @@ static void pci_epf_test_clean_dma_chan(struct pci_epf_test *epf_test)
 	if (!epf_test->dma_supported)
 		return;
 
-	dma_release_channel(epf_test->dma_chan_tx);
-	if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
+	if (epf_test->dma_chan_tx) {
+		dma_release_channel(epf_test->dma_chan_tx);
+		if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
+			epf_test->dma_chan_tx = NULL;
+			epf_test->dma_chan_rx = NULL;
+			return;
+		}
 		epf_test->dma_chan_tx = NULL;
-		epf_test->dma_chan_rx = NULL;
-		return;
 	}
 
-	dma_release_channel(epf_test->dma_chan_rx);
-	epf_test->dma_chan_rx = NULL;
+	if (epf_test->dma_chan_rx) {
+		dma_release_channel(epf_test->dma_chan_rx);
+		epf_test->dma_chan_rx = NULL;
+	}
 }
 
 static void pci_epf_test_print_rate(struct pci_epf_test *epf_test,
-- 
2.51.0