Hi,
On Friday 18 October 2013 03:46 AM, Jan Kara wrote:
Hello,
I was auditing get_user_pages() users and I've noticed that
omap_vout_uservirt_to_phys() is apparently called for arbitrary address
passed from userspace. If this address is in VM_IO vma, we use
vma->vm_pgoff for mapping the virtual address to a physical address.
However I don't think this is a generally valid computation for arbitrary
VM_IO vma. So do we expect vma to come from a particular source where this
is true? If yes, where do we expect vma comes from? Thanks for
clarification.
I don't know much about this domain, so I might be wrong here.
The function omap_vout_uservirt_to_phys() is used in the mode
'V4L2_MEMORY_USERPTR', to recieve a virtual address from the user.
The driver hardware only works with physically contiguous buffers. So
I'm guessing this vma maps to a buffer mmaped by the user application by
some other device(like a camera or something). This way, the user
doesn't need to copy the buffer between the 2 devices. I guess the
computation works in that case. We don't have any safety checks for this
though.
This driver is currenlty using the videobuf() framework, we would
eventually switch to videobuf2(), and hopefully this code shouldn't even
exist then.
Archit
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