vfio/type1: untag user pointers in vaddr_get_pfn

This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.

vaddr_get_pfn() uses provided user pointers for vma lookups, which can
only by done with untagged pointers.

Untag user pointers in this function.

Link: http://lkml.kernel.org/r/87422b4d72116a975896f2b19b00f38acbd28f33.1563904656.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <[email protected]>
Reviewed-by: Eric Auger <[email protected]>
Reviewed-by: Vincenzo Frascino <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: Jens Wiklander <[email protected]>
Cc: Khalid Aziz <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Mike Rapoport <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: xairy

drivers/vfio/vfio_iommu_type1.c

@@ -375,6 +375,8 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
 
 	down_read(&mm->mmap_sem);
 
+	vaddr = untagged_addr(vaddr);
+
 	vma = find_vma_intersection(mm, vaddr, vaddr + 1);
 
 	if (vma && vma->vm_flags & VM_PFNMAP) {