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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Christoph Hellwig <hch@lst.de>,
        Hillf Danton <hdanton@sina.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jeremy Linton <jeremy.linton@arm.com>,
        syzbot+353be47c9ce21b68b7ed@syzkaller.appspotmail.com,
        stable <stable@vger.kernel.org>
Subject: [PATCH] USB: usbfs: fix mmap dma mismatch
Date:   Thu, 14 May 2020 13:27:11 +0200
Message-Id: <20200514112711.1858252-1-gregkh@linuxfoundation.org>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.

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>
Reported-by: syzbot+353be47c9ce21b68b7ed@syzkaller.appspotmail.com
Fixes: 2bef9aed6f0e ("usb: usbfs: correct kernel->user page attribute mismatch")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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;
-- 
2.26.2