Re: [PATCH 2/2] mm/frame-vec: use FOLL_LONGTERM

[Jason Gunthorpe]

On Mon, Oct 05, 2020 at 02:38:54PM -0300, Jason Gunthorpe wrote:
> When get_vaddr_frames() does its hacky follow_pfn() loop it should never
> be allowed to extract a struct page from a normal VMA. This could allow a
> serious use-after-free problem on any kernel memory.
> 
> Restrict this to only work on VMA's with one of VM_IO | VM_PFNMAP
> set. This limits the use-after-free problem to only IO memory, which while
> still serious, is an improvement.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 8025e5ddf9c1 ("[media] mm: Provide new get_vaddr_frames() helper")
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
>  mm/frame_vector.c | 4 ++++
>  1 file changed, 4 insertions(+)

woops, this subject got badly corrupted when I was editing the CC
list, it was supposed to be:

[PATCH] mm/gpu: frame_vector: require all VMAs to be VM_PFNMAP

Andrew please let me know if you need a resend

Sorry,
Jason