mem->dma_handle is a dma address obtained by dma_alloc_coherent which
needn't be a physical address as a hardware IOMMU can (and most
likely will) return a bus address where physical != bus address. So
ensure we are remapping (remap_pfn_range) the right page in
__videobuf_mmap_mapper by using virt_to_phys(mem->vaddr) and not
mem->dma_handle.
While at it, use PFN_DOWN instead of explicit shift to obtain a frame
number.
This was discovered by a random review of the code when looking for
something completely different. I'm not aware of any bug reports for
this.
However it is a bug because many v4l drivers use this layer and have
no idea whether IOMMU is in the system and running or not.
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
This is a version with updated changelog.
drivers/media/video/videobuf-dma-contig.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/media/video/videobuf-dma-contig.c b/drivers/media/video/videobuf-dma-contig.c
index c969111..19d3e4a 100644
--- a/drivers/media/video/videobuf-dma-contig.c
+++ b/drivers/media/video/videobuf-dma-contig.c
@@ -300,7 +300,7 @@ static int __videobuf_mmap_mapper(struct videobuf_queue *q,
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
retval = remap_pfn_range(vma, vma->vm_start,
- mem->dma_handle >> PAGE_SHIFT,
+ PFN_DOWN(virt_to_phys(mem->vaddr))
size, vma->vm_page_prot);
if (retval) {
dev_err(q->dev, "mmap: remap failed with error %d. ", retval);
--
1.7.4.1
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