[PATCH 5.4 39/87] iavf: Fix handling of dummy receive descriptors

[Greg Kroah-Hartman]

From: Przemyslaw Patynowski <przemyslawx.patynowski@xxxxxxxxx>

[ Upstream commit a9f49e0060301a9bfebeca76739158d0cf91cdf6 ]

Fix memory leak caused by not handling dummy receive descriptor properly.
iavf_get_rx_buffer now sets the rx_buffer return value for dummy receive
descriptors. Without this patch, when the hardware writes a dummy
descriptor, iavf would not free the page allocated for the previous receive
buffer. This is an unlikely event but can still happen.

[Jesse: massaged commit message]

Fixes: efa14c398582 ("iavf: allow null RX descriptors")
Signed-off-by: Przemyslaw Patynowski <przemyslawx.patynowski@xxxxxxxxx>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>
Tested-by: Konrad Jankowski <konrad0.jankowski@xxxxxxxxx>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/ethernet/intel/iavf/iavf_txrx.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.c b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
index 7a30d5d5ef53..c6905d1b6182 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_txrx.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
@@ -1263,11 +1263,10 @@ static struct iavf_rx_buffer *iavf_get_rx_buffer(struct iavf_ring *rx_ring,
 {
 	struct iavf_rx_buffer *rx_buffer;
 
-	if (!size)
-		return NULL;
-
 	rx_buffer = &rx_ring->rx_bi[rx_ring->next_to_clean];
 	prefetchw(rx_buffer->page);
+	if (!size)
+		return rx_buffer;
 
 	/* we are reusing so sync this buffer for CPU use */
 	dma_sync_single_range_for_cpu(rx_ring->dev,
-- 
2.35.1