Re: [PATCH 2/2] uio: fix crash after the device is unregistered

[Xiubo Li]

On 2018/7/6 4:56, Jann Horn wrote:
> On Thu, Jul 5, 2018 at 10:53 PM <xiubli@xxxxxxxxxx> wrote:
> > From: Xiubo Li <xiubli@xxxxxxxxxx>
> >
> > For the target_core_user use case, after the device is unregistered
> > it maybe still opened in user space, then the kernel will crash, like:
> [...]
> > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> > ---
> >   drivers/uio/uio.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++--------
> >   1 file changed, 86 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> > index 33c3bfe..2b9268a 100644
> > --- a/drivers/uio/uio.c
> > +++ b/drivers/uio/uio.c
> [...]
> > @@ -720,30 +775,46 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
> >
> >          vma->vm_private_data = idev;
> >
> > +       mutex_lock(&idev->info_lock);
> > +       if (!idev->info) {
> > +               ret = -EINVAL;
> > +               goto out;
> > +       }
> > +
> >          mi = uio_find_mem_index(vma);
> > -       if (mi < 0)
> > -               return -EINVAL;
> > +       if (mi < 0) {
> > +               ret = -EINVAL;
> > +               goto out;
> > +       }
> >
> >          requested_pages = vma_pages(vma);
> >          actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK)
> >                          + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
> > -       if (requested_pages > actual_pages)
> > -               return -EINVAL;
> > +       if (requested_pages > actual_pages) {
> > +               ret = -EINVAL;
> > +               goto out;
> > +       }
> >
> >          if (idev->info->mmap) {
> >                  ret = idev->info->mmap(idev->info, vma);
> > -               return ret;
> > +               goto out;
> >          }
> >
> >          switch (idev->info->mem[mi].memtype) {
> >                  case UIO_MEM_PHYS:
> > -                       return uio_mmap_physical(vma);
> > +                       ret = uio_mmap_physical(vma);
> > +                       break;
> >                  case UIO_MEM_LOGICAL:
> >                  case UIO_MEM_VIRTUAL:
> > -                       return uio_mmap_logical(vma);
> > +                       ret = uio_mmap_logical(vma);
> > +                       break;
> >                  default:
> > -                       return -EINVAL;
> > +                       ret = -EINVAL;
> >          }
> > +
> > +out:
> > +       mutex_lock(&idev->info_lock);
> This is probably supposed to be mutex_unlock(...)?

Yeah yeah, right, Good catch :-)

Locally I had fixed this, but after my building and testing just forgot 
to amend it.

Will fix it.

Thanks very much.

BRs