Re: usbdev_mmap causes type confusion in page_table_check

[Christoph Hellwig]

On Sun, May 07, 2023 at 09:58:44PM +0800, Ruihan Li wrote:
> static int usbdev_mmap(struct file *file, struct vm_area_struct *vma)
> {
> 	// ...
> 	mem = usb_alloc_coherent(ps->dev, size, GFP_USER | __GFP_NOWARN,
> 			&dma_handle);
> 	// ...
> 	if (hcd->localmem_pool || !hcd_uses_dma(hcd)) {
> 		if (remap_pfn_range(vma, vma->vm_start,
> 				    virt_to_phys(usbm->mem) >> PAGE_SHIFT,

usb_alloc_coherent and up in the DMA coherent allocator (usually
anyway), and you absolutely must never do a virt_to_phys or virt_to_page
on that return value.  This code is a buggy as f**k.