On Mon, Mar 23, 2020 at 11:13:22AM +0000, Emil Velikov wrote:
> Hi Dan,
>
> On Fri, 20 Mar 2020 at 13:23, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
> >
> > If the "handles" allocation or the copy_from_user() fails then we leak
> > "objs". It's supposed to be freed in panfrost_job_cleanup().
> >
> > Fixes: c117aa4d8701 ("drm: Add a drm_gem_objects_lookup helper")
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > ---
> > drivers/gpu/drm/drm_gem.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> > index a9e4a610445a..f28724f2eb69 100644
> > --- a/drivers/gpu/drm/drm_gem.c
> > +++ b/drivers/gpu/drm/drm_gem.c
> > @@ -710,6 +710,8 @@ int drm_gem_objects_lookup(struct drm_file *filp, void __user *bo_handles,
> > if (!objs)
> > return -ENOMEM;
> >
> > + *objs_out = objs;
> > +
> > handles = kvmalloc_array(count, sizeof(u32), GFP_KERNEL);
> > if (!handles) {
> > ret = -ENOMEM;
> > @@ -723,8 +725,6 @@ int drm_gem_objects_lookup(struct drm_file *filp, void __user *bo_handles,
> > }
> >
> > ret = objects_lookup(filp, handles, count, objs);
> > - *objs_out = objs;
> > -
> > out:
> > kvfree(handles);
> > return ret;
>
> It seems that this will return error to the caller, mangle the output
> pointer and effectively still leak the objs.
The patch works.
This is "one function frees everything" style error handling. It gets
passed back to panfrost_ioctl_submit() which calls panfrost_job_put()
which calls panfrost_job_cleanup() which frees it.
It's a horrible way to do error handling but this was the only actual
bug I could see with the approach.
> Better option IMHO is to:
> - move the __user/copy_from_user into the caller
> Removes a silly kvmalloc_array(1,...) in ~90+ users and drops the "out" label.
> Extra bonus, this is the only instance in drm_gem with __user -
> consistency is nice.
> - add "err" or similar label, where the objs is freed before returning an error.
Those sound like good ideas. Also we could use kvcalloc() instead of
kvmalloc_array() with __GFP_ZERO. But it's too much for me to do...
I'm mostly focused on static analysis warnings.
regards,
dan carpenter
