It is a neat fix now, thank you.
On Sat, Sep 28, 2019 at 4:54 AM Hans de Goede <hdego...@redhat.com> wrote:
>
> Hi,
>
> On 28-09-2019 01:04, Navid Emamdoost wrote:
> > In hgcm_call_preprocess_linaddr memory is allocated for bounce_buf but
> > is not released if copy_form_user fails. The release is added.
> >
> > Fixes: 579db9d45cb4 ("virt: Add vboxguest VMMDEV communication code")
> >
> > Signed-off-by: Navid Emamdoost <navid.emamdo...@gmail.com>
>
> Thank you for catching this, I agree this is a bug, but I think we
> can fix it in a cleaner way (see below).
>
> > ---
> > drivers/virt/vboxguest/vboxguest_utils.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/virt/vboxguest/vboxguest_utils.c
> > b/drivers/virt/vboxguest/vboxguest_utils.c
> > index 75fd140b02ff..7965885a50fa 100644
> > --- a/drivers/virt/vboxguest/vboxguest_utils.c
> > +++ b/drivers/virt/vboxguest/vboxguest_utils.c
> > @@ -222,8 +222,10 @@ static int hgcm_call_preprocess_linaddr(
> >
> > if (copy_in) {
> > ret = copy_from_user(bounce_buf, (void __user *)buf, len);
> > - if (ret)
> > + if (ret) {
> > + kvfree(bounce_buf);
> > return -EFAULT;
> > + }
> > } else {
> > memset(bounce_buf, 0, len);
> > }
> >
>
> First let me quote some more of the function, pre leak fix, for context:
>
> bounce_buf = kvmalloc(len, GFP_KERNEL);
> if (!bounce_buf)
> return -ENOMEM;
>
> if (copy_in) {
> ret = copy_from_user(bounce_buf, (void __user *)buf, len);
> if (ret)
> return -EFAULT;
> } else {
> memset(bounce_buf, 0, len);
> }
>
> *bounce_buf_ret = bounce_buf;
>
> This function gets called repeatedly by hgcm_call_preprocess(), and the
> caller of hgcm_call_preprocess() already takes care of freeing the
> bounce bufs both on a (later) error and on success:
>
> ret = hgcm_call_preprocess(parms, parm_count, &bounce_bufs, &size);
> if (ret) {
> /* Even on error bounce bufs may still have been allocated */
> goto free_bounce_bufs;
> }
>
> ...
>
> free_bounce_bufs:
> if (bounce_bufs) {
> for (i = 0; i < parm_count; i++)
> kvfree(bounce_bufs[i]);
> kfree(bounce_bufs);
> }
>
> So we are already taking care of freeing bounce-bufs allocated for previous
> parameters to the call (which me must do anyways), so a cleaner fix would
> be to store the allocated bounce_buf in the bounce_bufs array before
> doing the copy_from_user, then if copy_from_user fails it will be cleaned
> up by the code at the free_bounce_bufs label.
>
> IOW I believe it is better to fix this by changing the part of
> hgcm_call_preprocess_linaddr I quoted to:
>
> bounce_buf = kvmalloc(len, GFP_KERNEL);
> if (!bounce_buf)
> return -ENOMEM;
>
> *bounce_buf_ret = bounce_buf;
>
> if (copy_in) {
> ret = copy_from_user(bounce_buf, (void __user *)buf, len);
> if (ret)
> return -EFAULT;
> } else {
> memset(bounce_buf, 0, len);
> }
>
> This should also fix the leak in IMHO is a clear way of doing so.
>
> Regards,
>
> Hans
>
>
>
>
>
--
Navid.
