[PATCH 5.5 199/399] ice: add extra check for null Rx descriptor

Greg Kroah-Hartman
2020-02-21T07:53:52Z

From: Mitch Williams <mitch.a.williams@intel.com>

[ Upstream commit 1f45ebe0d8fbe6178670b663005f38ef8535db5d ]

In the case where the hardware gives us a null Rx descriptor, it is
theoretically possible that we could call one of our skb-construction
functions with no data pointer, which would cause a panic.

In real life, this will never happen - we only get null RX
descriptors as the final descriptor in a chain of otherwise-valid
descriptors. When this happens, the skb will be extant and we'll just
call ice_add_rx_frag(), which can deal with empty data buffers.

Unfortunately, Coverity does not have intimate knowledge of our
hardware, so we must add a check here.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/intel/ice/ice_txrx.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 2c212f64d99f2..8b2b9e254d28d 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -1071,13 +1071,16 @@ static int ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
ice_put_rx_buf(rx_ring, rx_buf);
continue;
construct_skb:
- if (skb)
+ if (skb) {
ice_add_rx_frag(rx_ring, rx_buf, skb, size);
- else if (ice_ring_uses_build_skb(rx_ring))
- skb = ice_build_skb(rx_ring, rx_buf, &xdp);
- else
+ } else if (likely(xdp.data)) {
+ if (ice_ring_uses_build_skb(rx_ring))
+ skb = ice_build_skb(rx_ring, rx_buf, &xdp);
+ else
+ skb = ice_construct_skb(rx_ring, rx_buf, &xdp);
+ } else {
skb = ice_construct_skb(rx_ring, rx_buf, &xdp);
-
+ }
/* exit if we failed to retrieve a buffer */
if (!skb) {
rx_ring->rx_stats.alloc_buf_failed++;
--
2.20.1