[PATCH] vhost: fix possible null pointer dereference

[Maxime Coquelin <maxime.coquelin@redhat.com>]

When handling VHOST_USER_SET_MEM_TABLE request ending
up in changing existing memory map, a device's memory
pointer may ends up being dereference while being NULL in
IOTLB cache flush function.

Coverity issue: 383646
Fixes: dea092d0addb ("vhost: fix madvise arguments alignment")

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/vhost/vhost_user.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 9e361082dc..23a6a4e2bd 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -1355,16 +1355,16 @@ vhost_user_set_mem_table(struct virtio_net **pdev,
 			async_notify = true;
 		}
 
+		/* Flush IOTLB cache as previous HVAs are now invalid */
+		if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
+			for (i = 0; i < dev->nr_vring; i++)
+				vhost_user_iotlb_flush_all(dev, dev->virtqueue[i]);
+
 		free_mem_region(dev);
 		rte_free(dev->mem);
 		dev->mem = NULL;
 	}
 
-	/* Flush IOTLB cache as previous HVAs are now invalid */
-	if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM))
-		for (i = 0; i < dev->nr_vring; i++)
-			vhost_user_iotlb_flush_all(dev, dev->virtqueue[i]);
-
 	/*
 	 * If VQ 0 has already been allocated, try to allocate on the same
 	 * NUMA node. It can be reallocated later in numa_realloc().
-- 
2.39.2