4.17-stable review patch. If anyone has any objections, please let me know.
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From: Jason Gunthorpe jgg@mellanox.com
commit bb94b55af3461e26b32f0e23d455abeae0cfca5d upstream.
The patch noted in the fixes below converted get_user_pages_fast() to get_user_pages_longterm(), however the two calls differ in a few ways.
First _fast() is documented to not require the mmap_sem, while _longterm() is documented to need it. Hold the mmap sem as required.
Second, _fast accepts an 'int write' while _longterm uses 'unsigned int gup_flags', so the expression '!!(prot & IOMMU_WRITE)' is only working by luck as FOLL_WRITE is currently == 0x1. Use the expected FOLL_WRITE constant instead.
Fixes: 94db151dc892 ("vfio: disable filesystem-dax page pinning") Cc: stable@vger.kernel.org Signed-off-by: Jason Gunthorpe jgg@mellanox.com Acked-by: Dan Williams dan.j.williams@intel.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/vfio/vfio_iommu_type1.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-)
--- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -346,18 +346,16 @@ static int vaddr_get_pfn(struct mm_struc struct page *page[1]; struct vm_area_struct *vma; struct vm_area_struct *vmas[1]; + unsigned int flags = 0; int ret;
+ if (prot & IOMMU_WRITE) + flags |= FOLL_WRITE; + + down_read(&mm->mmap_sem); if (mm == current->mm) { - ret = get_user_pages_longterm(vaddr, 1, !!(prot & IOMMU_WRITE), - page, vmas); + ret = get_user_pages_longterm(vaddr, 1, flags, page, vmas); } else { - unsigned int flags = 0; - - if (prot & IOMMU_WRITE) - flags |= FOLL_WRITE; - - down_read(&mm->mmap_sem); ret = get_user_pages_remote(NULL, mm, vaddr, 1, flags, page, vmas, NULL); /* @@ -371,8 +369,8 @@ static int vaddr_get_pfn(struct mm_struc ret = -EOPNOTSUPP; put_page(page[0]); } - up_read(&mm->mmap_sem); } + up_read(&mm->mmap_sem);
if (ret == 1) { *pfn = page_to_pfn(page[0]);