Re: [PATCH-for-8.0? v1] hw/pvrdma: Protect against buggy or malicious guest driver

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 1/3/23 15:29, Yuval Shaia wrote:
> Guest driver allocates and initialize page tables to be used as a ring
> of descriptors for CQ and async events.
> The page table that represents the ring, along with the number of pages
> in the page table is passed to the device.
> Currently our device supports only one page table for a ring.
> 
> Let's make sure that the number of page table entries the driver
> reports, do not exceeds the one page table size.
> 

Fixes: CVE-2023-1544

> Reported-by: Soul Chen <soulchen8650@gmail.com>
> Signed-off-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
> ---
> v0 -> v1:
> 	* Take ring-state into account
> 	* Add Reported-by
> ---
>   hw/rdma/vmw/pvrdma_main.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/rdma/vmw/pvrdma_main.c b/hw/rdma/vmw/pvrdma_main.c
> index 4fc6712025..55b338046e 100644
> --- a/hw/rdma/vmw/pvrdma_main.c
> +++ b/hw/rdma/vmw/pvrdma_main.c
> @@ -91,19 +91,33 @@ static int init_dev_ring(PvrdmaRing *ring, PvrdmaRingState **ring_state,
>                            dma_addr_t dir_addr, uint32_t num_pages)
>   {
>       uint64_t *dir, *tbl;
> -    int rc = 0;
> +    int max_pages, rc = 0;
>   
>       if (!num_pages) {
>           rdma_error_report("Ring pages count must be strictly positive");
>           return -EINVAL;
>       }
>   
> +    /*
> +     * Make sure we can satisfy the requested number of pages in a single
> +     * TARGET_PAGE_SIZE sized page table (taking into account that first entry
> +     * is reserved for ring-state)
> +     */

Worth a definition? Or maybe better an enum.

> +    max_pages = TARGET_PAGE_SIZE / sizeof(dma_addr_t) - 1;

Possibly clearer as a #define in pvrdma_dev_ring.h.

> +    if (num_pages > max_pages) {
> +        rdma_error_report("Maximum pages on a single directory must not exceed %d\n",
> +                          max_pages);
> +        return -EINVAL;
> +    }
> +
>       dir = rdma_pci_dma_map(pci_dev, dir_addr, TARGET_PAGE_SIZE);
>       if (!dir) {
>           rdma_error_report("Failed to map to page directory (ring %s)", name);
>           rc = -ENOMEM;
>           goto out;
>       }
> +
> +    /* We support only one page table for a ring */
>       tbl = rdma_pci_dma_map(pci_dev, dir[0], TARGET_PAGE_SIZE);
>       if (!tbl) {
>           rdma_error_report("Failed to map to page table (ring %s)", name);

Now looking at the following pvrdma_ring_init() call, I see too many
magic values for my taste, so feel unsafe to review:

     /* RX ring is the second */
     (*ring_state)++;
     rc = pvrdma_ring_init(ring, name, pci_dev,
                           (PvrdmaRingState *)*ring_state,
                           (num_pages - 1) * TARGET_PAGE_SIZE /
                           sizeof(struct pvrdma_cqne),
                           sizeof(struct pvrdma_cqne),
                           (dma_addr_t *)&tbl[1],
                           (dma_addr_t)num_pages - 1);