When hcd->localmem_pool is non-null, it is used to allocate DMA memory. In this case, the dma address will be properly returned (in dma_handle), and dma_mmap_coherent should be used to map this memory into the user space. However, the current implementation uses pfn_remap_range, which is supposed to map normal pages (instead of DMA pages).
Instead of repeating the logic in the memory allocation function, this patch introduces a more robust solution. To address the previous issue, this patch checks the type of allocated memory by testing whether dma_handle is properly set. If dma_handle is properly returned, it means some DMA pages are allocated and dma_mmap_coherent should be used to map them. Otherwise, normal pages are allocated and pfn_remap_range should be called. This ensures that the correct mmap functions are used consistently, independently with logic details that determine which type of memory gets allocated.
Fixes: a0e710a7def4 ("USB: usbfs: fix mmap dma mismatch") Cc: stable@vger.kernel.org Signed-off-by: Ruihan Li lrh2000@pku.edu.cn --- drivers/usb/core/devio.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index b4cf9e860..5067030b7 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -235,7 +235,7 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) size_t size = vma->vm_end - vma->vm_start; void *mem; unsigned long flags; - dma_addr_t dma_handle; + dma_addr_t dma_handle = DMA_MAPPING_ERROR; int ret;
ret = usbfs_increase_memory_usage(size + sizeof(struct usb_memory)); @@ -265,7 +265,13 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma) usbm->vma_use_count = 1; INIT_LIST_HEAD(&usbm->memlist);
- if (hcd->localmem_pool || !hcd_uses_dma(hcd)) { + /* In DMA-unavailable cases, hcd_buffer_alloc_pages allocates + * normal pages and assigns DMA_MAPPING_ERROR to dma_handle. Check + * whether we are in such cases, and then use remap_pfn_range (or + * dma_mmap_coherent) to map normal (or DMA) pages into the user + * space, respectively. + */ + if (dma_handle == DMA_MAPPING_ERROR) { if (remap_pfn_range(vma, vma->vm_start, virt_to_phys(usbm->mem) >> PAGE_SHIFT, size, vma->vm_page_prot) < 0) {