[PATCH] IB/hfi1: Fix possible null-pointer dereference in _extend_sdma_tx_descs()

[Tuo Li]

kmalloc_array() is called to allocate memory for tx->descp. If it fails, 
the function __sdma_txclean() is called:
  __sdma_txclean(dd, tx);

However, in the function __sdma_txclean(), tx-descp is dereferenced if 
tx->num_desc is not zero:
  sdma_unmap_desc(dd, &tx->descp[0]);

To fix this possible null-pointer dereference, assign 0 to tx->num_desc if
kmalloc_array() returns NULL.

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
---
 drivers/infiniband/hw/hfi1/sdma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/hfi1/sdma.c b/drivers/infiniband/hw/hfi1/sdma.c
index eb15c310d63d..00e29c3dfe96 100644
--- a/drivers/infiniband/hw/hfi1/sdma.c
+++ b/drivers/infiniband/hw/hfi1/sdma.c
@@ -3079,8 +3079,10 @@ static int _extend_sdma_tx_descs(struct hfi1_devdata *dd, struct sdma_txreq *tx)
 			MAX_DESC,
 			sizeof(struct sdma_desc),
 			GFP_ATOMIC);
-	if (!tx->descp)
+	if (!tx->descp) {
+		tx->num_desc = 0;
 		goto enomem;
+	}
 
 	/* reserve last descriptor for coalescing */
 	tx->desc_limit = MAX_DESC - 1;
-- 
2.25.1