ivshmem: fix crash in corner case

Depending on the configured segments it is possible to hit a
segmentation fault as a result of decrementing an unsigned index with
value 0.

To avoid it, exit the loop if the index has value 0.

Fixes: 40b966a211ab ("ivshmem: library changes for mmaping using ivshmem")
Signed-off-by: Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com>

diff --git a/lib/librte_ivshmem/rte_ivshmem.c b/lib/librte_ivshmem/rte_ivshmem.c
index 7ca55edb91b891a2836615cc7d6f2c1e0289be31..9621906d07f82eaa9617da10c0dff3a29ae11639 100644 (file)
--- a/lib/librte_ivshmem/rte_ivshmem.c
+++ b/lib/librte_ivshmem/rte_ivshmem.c
@@ -377,6 +377,8 @@ build_config(struct rte_ivshmem_metadata * metadata)
                        for (j = biggest_idx - 1; j >= i; j--) {
                                memcpy(&pages[j+1], &pages[j], sizeof(struct rte_memseg));
                                memset(&pages[j], 0, sizeof(struct rte_memseg));
+                               if (j == 0)
+                                       break;
                        }
 
                        /* put old biggest segment to its new place */