[PATCH 5.6 137/194] USB: usbfs: fix mmap dma mismatch

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

commit a0e710a7def471b8eb779ff551fc27701da49599 upstream.

In commit 2bef9aed6f0e ("usb: usbfs: correct kernel->user page attribute
mismatch") we switched from always calling remap_pfn_range() to call
dma_mmap_coherent() to handle issues with systems with non-coherent USB host
controller drivers.  Unfortunatly, as syzbot quickly told us, not all the world
is host controllers with DMA support, so we need to check what host controller
we are attempting to talk to before doing this type of allocation.

Thanks to Christoph for the quick idea of how to fix this.

Fixes: 2bef9aed6f0e ("usb: usbfs: correct kernel->user page attribute mismatch")
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jeremy Linton <jeremy.linton@xxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Reported-by: syzbot+353be47c9ce21b68b7ed@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Jeremy Linton <jeremy.linton@xxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Link: https://lore.kernel.org/r/20200514112711.1858252-1-gregkh@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/core/devio.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -251,9 +251,19 @@ static int usbdev_mmap(struct file *file
 	usbm->vma_use_count = 1;
 	INIT_LIST_HEAD(&usbm->memlist);
 
-	if (dma_mmap_coherent(hcd->self.sysdev, vma, mem, dma_handle, size)) {
-		dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
-		return -EAGAIN;
+	if (hcd->localmem_pool || !hcd_uses_dma(hcd)) {
+		if (remap_pfn_range(vma, vma->vm_start,
+				    virt_to_phys(usbm->mem) >> PAGE_SHIFT,
+				    size, vma->vm_page_prot) < 0) {
+			dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
+			return -EAGAIN;
+		}
+	} else {
+		if (dma_mmap_coherent(hcd->self.sysdev, vma, mem, dma_handle,
+				      size)) {
+			dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
+			return -EAGAIN;
+		}
 	}
 
 	vma->vm_flags |= VM_IO;