[dpdk-dev] [PATCH] ethdev: fix rte_eth_dev_xstats_get with NULL

[Stephen Hemminger <stephen@networkplumber.org>]

Normal usage of rte_eth_dev_xstats_get is to call twice. The
first time the function is called with portid, xstats = NULL
and n = 0; this returns the number of entries in the statistics
table that need to be allocated.

The problem is that the routine adds a count value to NULL (0)
and assumes that this is a valid pointer (it isn't). Device drivers
all have a check for NULL, and this no longer matches.

Bug was introduced by commit d4fef8b0d5e5
("ethdev: expose generic and driver specific stats in xstats")

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/librte_ether/rte_ethdev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
index db35102..8721a6b 100644
--- a/lib/librte_ether/rte_ethdev.c
+++ b/lib/librte_ether/rte_ethdev.c
@@ -1495,8 +1495,9 @@ rte_eth_xstats_get(uint8_t port_id, struct rte_eth_xstats *xstats,
 		/* Retrieve the xstats from the driver at the end of the
 		 * xstats struct.
 		 */
-		xcount = (*dev->dev_ops->xstats_get)(dev, &xstats[count],
-			 (n > count) ? n - count : 0);
+		xcount = (*dev->dev_ops->xstats_get)(dev,
+				     xstats ? xstats + count : NULL,
+				     (n > count) ? n - count : 0);
 
 		if (xcount < 0)
 			return xcount;
-- 
2.1.4