From a0e710a7def471b8eb779ff551fc27701da49599 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Thu, 14 May 2020 13:27:11 +0200
Subject: [PATCH] USB: usbfs: fix mmap dma mismatch
Git-commit: a0e710a7def471b8eb779ff551fc27701da49599
Patch-mainline: v5.7-rc6
References: git-fixes

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@lst.de>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: stable <stable@vger.kernel.org>
Reported-by: syzbot+353be47c9ce21b68b7ed@syzkaller.appspotmail.com
Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20200514112711.1858252-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index b9db9812d6c5..d93d94d7ff50 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -251,9 +251,19 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma)
 	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;
-- 
2.16.4