[PATCH] vhost: fix possible null pointer dereference

[Xia, Chenbo]

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin at redhat.com>
> Sent: Thursday, March 9, 2023 7:37 PM
> To: dev at dpdk.org; mkp at redhat.com; Xia, Chenbo <chenbo.xia at intel.com>;
> david.marchand at redhat.com
> Cc: Maxime Coquelin <maxime.coquelin at redhat.com>
> Subject: [PATCH] vhost: fix possible null pointer dereference
> 
> 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 at 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

Reviewed-by: Chenbo Xia <chenbo.xia at intel.com>