linux-kernel - Re: [PATCH] drm/v3d: Fix memory leak in v3d_submit_cl

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Date:   Tue, 22 Oct 2019 22:53:57 -0500
From:   Navid Emamdoost <navid.emamdoost@...il.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     Navid Emamdoost <emamd001@....edu>, Kangjie Lu <kjlu@....edu>,
        Stephen McCamant <smccaman@....edu>,
        Eric Anholt <eric@...olt.net>, David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/v3d: Fix memory leak in v3d_submit_cl_ioctl

On Tue, Oct 22, 2019 at 4:36 AM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Mon, Oct 21, 2019 at 01:52:49PM -0500, Navid Emamdoost wrote:
> > In the impelementation of v3d_submit_cl_ioctl() there are two memory
> > leaks. One is when allocation for bin fails, and the other is when bin
> > initialization fails. If kcalloc fails to allocate memory for bin then
> > render->base should be put. Also, if v3d_job_init() fails to initialize
> > bin->base then allocated memory for bin should be released.
> >
> > Fixes: a783a09ee76d ("drm/v3d: Refactor job management.")
> > Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
> > ---
> >  drivers/gpu/drm/v3d/v3d_gem.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> > index 5d80507b539b..19c092d75266 100644
> > --- a/drivers/gpu/drm/v3d/v3d_gem.c
> > +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> > @@ -557,13 +557,16 @@ v3d_submit_cl_ioctl(struct drm_device *dev, void *data,
> >
> >       if (args->bcl_start != args->bcl_end) {
> >               bin = kcalloc(1, sizeof(*bin), GFP_KERNEL);
> > -             if (!bin)
> > +             if (!bin) {
> > +                     v3d_job_put(&render->base);
>
> The job isn't initialized yet, this doesn't work.
Do you mean we have to release render via kfree() here?

>
> >                       return -ENOMEM;
> > +             }
> >
> >               ret = v3d_job_init(v3d, file_priv, &bin->base,
> >                                  v3d_job_free, args->in_sync_bcl);
> >               if (ret) {
> >                       v3d_job_put(&render->base);
>
> v3d_job_put will call kfree, if you chase the callchain long enough (in
> v3d_job_free). So no bug here, this would lead to a double kfree and
> crash.
Yes, v3d_job_put() takes care of render,

> -Daniel
>
> > +                     kfree(bin);
but how about leaking bin?

> >                       return ret;
> >               }
> >
> > --
> > 2.17.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch



-- 
Navid.