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: [e-mail]
Signed-off-by: Iwona Winiarska <[e-mail]>
Reviewed-by: Andrew Jeffery <[e-mail]>
Tested-by: Andrew Jeffery <[e-mail]>
Reviewed-by: Joel Stanley <[e-mail]>
Signed-off-by: Joel Stanley <[e-mail]>

drivers/soc/aspeed/aspeed-lpc-ctrl.c

···
 	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 */