Re: [PATCH v2] media: meson: vdec: Fix a NULL pointer dereference in amvdec_add_ts()

Greg Kroah-Hartman
2021-12-14T14:18:22Z

On Tue, Dec 14, 2021 at 02:46:13PM +0100, Mauro Carvalho Chehab wrote:
> Em Fri, 3 Dec 2021 00:03:57 +0800
> Zhou Qingyang <zhou1615@umn.edu> escreveu:
>
> > In amvdec_add_ts(), there is a dereference of kzalloc(), which could lead
> > to a NULL pointer dereference on failure of kzalloc().
> >
> > I fix this bug by adding a NULL check of new_ts.
> >
> > This bug was found by a static analyzer. The analysis employs
> > differential checking to identify inconsistent security operations
> > (e.g., checks or kfrees) between two code paths and confirms that the
> > inconsistent operations are not recovered in the current function or
> > the callers, so they constitute bugs.
> >
> > Note that, as a bug found by static analysis, it can be a false
> > positive or hard to trigger. Multiple researchers have cross-reviewed
> > the bug.
> >
> > Builds with CONFIG_VIDEO_MESON_VDEC=m show no new warnings,
> > and our static analyzer no longer warns about this code.
> >
> > Fixes: 876f123b8956 ("media: meson: vdec: bring up to compliance")
> > Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
> > ---
> > Changes in v2:
> > - Delete dev_err() message
> >
> > drivers/staging/media/meson/vdec/vdec_helpers.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > index b9125c295d1d..ac60514c475b 100644
> > --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> > +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> > @@ -234,6 +234,9 @@ void amvdec_add_ts(struct amvdec_session *sess, u64 ts,
> > unsigned long flags;
> >
> > new_ts = kzalloc(sizeof(*new_ts), GFP_KERNEL);
> > + if (!new_ts)
> > + return;
> > +
> > new_ts->ts = ts;
> > new_ts->tc = tc;
> > new_ts->offset = offset;
>
> I don't think this change is ok. Sure, it needs to check if
> kzalloc() fails, but it should return -ENOMEM and the caller
> should check if it returns an error. So, I would expect
> that this patch would also touch the caller function at
> drivers/staging/media/meson/vdec/esparser.c.

This is why umn.edu emails still are in my black-hole :(