hw/pvrdma: Protect against buggy or malicious guest driver

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.

Reported-by: Soul Chen <soulchen8650@gmail.com>
Signed-off-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
Fixes: CVE-2023-1544
Message-ID: <20230301142926.18686-1-yuval.shaia.ml@gmail.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 85fc35a)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

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