[PATCH] dma-buf: Fix NULL pointer dereference in sanitycheck()

[Pavel Sakharov]

If due to a memory allocation failure mock_chain() returns NULL, it is
passed to dma_fence_enable_sw_signaling() resulting in NULL pointer
dereference there.

Call dma_fence_enable_sw_signaling() only if mock_chain() succeeds.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d62c43a953ce ("dma-buf: Enable signaling on fence for selftests")
Signed-off-by: Pavel Sakharov <p.sakharov@xxxxxxxxx>

---
 drivers/dma-buf/st-dma-fence-chain.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 9c2a0c082a76..ed4b323886e4 100644
--- a/drivers/dma-buf/st-dma-fence-chain.c
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -84,11 +84,11 @@ static int sanitycheck(void *arg)
 		return -ENOMEM;

 	chain = mock_chain(NULL, f, 1);
-	if (!chain)
+	if (chain)
+		dma_fence_enable_sw_signaling(chain);
+	else
 		err = -ENOMEM;

-	dma_fence_enable_sw_signaling(chain);
-
 	dma_fence_signal(f);
 	dma_fence_put(f);

--
2.44.0