[PATCH] hw/rdma: Fix possible mremap overflow in the pvrdma device (CVE-2021-3582)

[Marcel Apfelbaum]

From: Marcel Apfelbaum <marcel@redhat.com>

Ensure mremap boundaries not trusting the guest kernel to
pass the correct buffer length.

Fixes: CVE-2021-3582
Reported-by: VictorV (Kunlun Lab) <vv474172261@gmail.com>
Tested-by: VictorV (Kunlun Lab) <vv474172261@gmail.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
---
 hw/rdma/vmw/pvrdma_cmd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/rdma/vmw/pvrdma_cmd.c b/hw/rdma/vmw/pvrdma_cmd.c
index f59879e257..dadab4966b 100644
--- a/hw/rdma/vmw/pvrdma_cmd.c
+++ b/hw/rdma/vmw/pvrdma_cmd.c
@@ -38,6 +38,12 @@ static void *pvrdma_map_to_pdir(PCIDevice *pdev, uint64_t 
pdir_dma,
         return NULL;
     }
 
+    length = ROUND_UP(length, TARGET_PAGE_SIZE);
+    if (nchunks * TARGET_PAGE_SIZE != length) {
+        rdma_error_report("Invalid nchunks/length (%u, %lu)", nchunks, length);
+        return NULL;
+    }
+
     dir = rdma_pci_dma_map(pdev, pdir_dma, TARGET_PAGE_SIZE);
     if (!dir) {
         rdma_error_report("Failed to map to page directory");
-- 
2.17.2