vm audit: add VM_DONTEXPAND to mmap for drivers that need it

Drivers that register a ->fault handler, but do not range-check the
offset argument, must set VM_DONTEXPAND in the vm_flags in order to
prevent an expanding mremap from overflowing the resource.

I've audited the tree and attempted to fix these problems (usually by
adding VM_DONTEXPAND where it is not obvious).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 1 deletions

diff --git a/drivers/char/drm/drm_vm.c b/drivers/char/drm/drm_vm.c
index e8d50af58201..ef5e6b130c48 100644
--- a/drivers/char/drm/drm_vm.c
+++ b/drivers/char/drm/drm_vm.c
@@ -506,6 +506,7 @@ static int drm_mmap_dma(struct file *filp, struct vm_area_struct *vma)
         vma->vm_ops = &drm_vm_dma_ops;
 
         vma->vm_flags |= VM_RESERVED;   /* Don't swap */
+        vma->vm_flags |= VM_DONTEXPAND;
 
         vma->vm_file = filp;    /* Needed for drm_vm_open() */
         drm_vm_open_locked(vma);
@@ -655,6 +656,7 @@ static int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
                 return -EINVAL; /* This should never happen. */
         }
         vma->vm_flags |= VM_RESERVED;   /* Don't swap */
+        vma->vm_flags |= VM_DONTEXPAND;
 
         vma->vm_file = filp;    /* Needed for drm_vm_open() */
         drm_vm_open_locked(vma);
diff --git a/drivers/char/mspec.c b/drivers/char/mspec.c
index 82f2e27dca7d..ff146c2b08fd 100644
--- a/drivers/char/mspec.c
+++ b/drivers/char/mspec.c
@@ -283,7 +283,7 @@ mspec_mmap(struct file *file, struct vm_area_struct *vma,
         vdata->refcnt = ATOMIC_INIT(1);
         vma->vm_private_data = vdata;
 
-        vma->vm_flags |= (VM_IO | VM_RESERVED | VM_PFNMAP);
+        vma->vm_flags |= (VM_IO | VM_RESERVED | VM_PFNMAP | VM_DONTEXPAND);
         if (vdata->type == MSPEC_FETCHOP || vdata->type == MSPEC_UNCACHED)
                 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
         vma->vm_ops = &mspec_vm_ops;