soc: aspeed: lpc-ctrl: Fix boundary check for mmap

The check mixes pages (vm_pgoff) with bytes (vm_start, vm_end) on one
side of the comparison, and uses resource address (rather than just the
resource size) on the other side of the comparison.
This can allow malicious userspace to easily bypass the boundary check and
map pages that are located outside memory-region reserved by the driver.

Fixes: 6c4e97678501 ("drivers/misc: Add Aspeed LPC control driver")
Cc: stable@vger.kernel.org
Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Tested-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@aj.id.au>
Signed-off-by: Joel Stanley <joel@jms.id.au>

diff --git a/drivers/soc/aspeed/aspeed-lpc-ctrl.c b/drivers/soc/aspeed/aspeed-lpc-ctrl.c
index c557ffd0992c7760555bc4754aefe8bd00db1c6e..55e46fa6cf42413d2645ff5024e729845dabf833 100644 (file)
--- a/drivers/soc/aspeed/aspeed-lpc-ctrl.c
+++ b/drivers/soc/aspeed/aspeed-lpc-ctrl.c
@@ -51,7 +51,7 @@ static int aspeed_lpc_ctrl_mmap(struct file *file, struct vm_area_struct *vma)
        unsigned long vsize = vma->vm_end - vma->vm_start;
        pgprot_t prot = vma->vm_page_prot;
 
-       if (vma->vm_pgoff + vsize > lpc_ctrl->mem_base + lpc_ctrl->mem_size)
+       if (vma->vm_pgoff + vma_pages(vma) > lpc_ctrl->mem_size >> PAGE_SHIFT)
                return -EINVAL;
 
        /* ast2400/2500 AHB accesses are not cache coherent */