Re: [dpdk-dev] [PATCH] vhost: catch overflow causing mmap of size 0

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Jan 16, 2020 at 11:44:27AM +0100, Maxime Coquelin wrote:
> This patch catches an overflow that could happen if an
> invalid region size or page alignement is provided by the

s/alignement/alignment/

> guest via the VHOST_USER_SET_MEM_TABLE request.
> 
> If the sum of the size to mmap and the alignment overflows
> uint64_t, then RTE_ALIGN_CEIL(mmap_size, alignment) macro
> will return 0. This value was passed as is as size argument
> to mmap().
> 
> While kernel handling of mmap() syscall returns an error
> if size is 0, it is better to catch it earlier and provide
> a meaningful error log.
> 
> Fixes: ec09c280b839 ("vhost: fix mmap not aligned with hugepage size")
> Cc: stable@dpdk.org
> 
> Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  lib/librte_vhost/vhost_user.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 0b7d1e288e..41ec069cb6 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -1145,6 +1145,21 @@ vhost_user_set_mem_table(struct virtio_net **pdev, struct VhostUserMsg *msg,
>  			goto err_mmap;
>  		}
>  		mmap_size = RTE_ALIGN_CEIL(mmap_size, alignment);
> +		if (mmap_size == 0) {
> +			/*
> +			 * It could happen if initial mmap_size + alignment
> +			 * overflows the sizeof uint64, which could happen if
> +			 * either mmap_size or alignment value is wrong.
> +			 *
> +			 * mmap() kernel implementation would return an error,
> +			 * but better catch it before and provide useful info
> +			 * in the logs.
> +			 */
> +			VHOST_LOG_CONFIG(ERR, "mmap size (0x%" PRIx64 ") "
> +					"or alignment (0x%" PRIx64 ") is invalid\n",
> +					reg->size + mmap_offset, alignment);
> +			goto err_mmap;
> +		}
>  
>  		populate = (dev->dequeue_zero_copy) ? MAP_POPULATE : 0;
>  		mmap_addr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
> -- 
> 2.21.0

Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>