This is a note to let you know that I've just added the patch titled

USB: usbfs: fix mmap dma mismatch

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

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: USB: usbfs: fix mmap dma mismatch

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.or... 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;