On Thu, May 14, 2020 at 08:31:58AM +0200, Christoph Hellwig wrote: > On Thu, May 14, 2020 at 08:27:50AM +0200, Greg KH wrote: > > On Thu, May 14, 2020 at 08:14:17AM +0200, Christoph Hellwig wrote: > > > Guys, can you please start formal thread on this? I have no > > > idea where this came from and what the rationale is. Btw, if the > > > pfn is crap in dma_direct_mmap then the dma_addr_t passed in is > > > crap, as it is derived from that. What is the caller, and how is > > > this triggered? > > > > > > Ok, to summarize, commit 2bef9aed6f0e ("usb: usbfs: correct kernel->user > > page attribute mismatch") changed a call from remap_pfn_range() to > > dma_mmap_coherent() for usb data buffers being sent from userspace. > > I only need to look at the commit for 3 seconds to tell you that it is > completely buggy. While using dma_mmap_coherent is fundamentally the > right thing and absolutely required for dma_alloc_* allocations, USB > also uses it's own local gen pool allocator or plain kmalloc for not > DMA capable controller. This need to use remap_pfn_range. I'm pretty > sure you hit one of those cases. > > The logic should be something like: > > if (hcd->localmem_pool || !hcd_uses_dma(hcd)) > remap_pfn_range() > else > dma_mmap_coherent() Ok, that's simple enough, patch is below. Jeremy, any objection to this change? thanks, greg k-h 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;