ethdev: fix xstats size query with NULL

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.

Fixes: d4fef8b0d5e5 ("ethdev: expose generic and driver specific stats in xstats")

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Olivier Matz <olivier.matz@6wind.com>

diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
index db35102..8721a6b 100644 (file)
--- 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;