Re: [PATCH] clk: fix a missing-free bug in clk_cpy_name()
From: Stephen Boyd
Date: Thu Jun 06 2019 - 16:21:05 EST
Quoting Gen Zhang (2019-06-05 09:00:43)
> On Wed, Jun 05, 2019 at 08:38:00AM +0200, Jiri Slaby wrote:
> > On 31. 05. 19, 3:14, Gen Zhang wrote:
> > > In clk_cpy_name(), '*dst_p'('parent->name'and 'parent->fw_name') and
> > > 'dst' are allcoted by kstrdup_const(). According to doc: "Strings
> > > allocated by kstrdup_const should be freed by kfree_const". So
> > > 'parent->name', 'parent->fw_name' and 'dst' should be freed.
> > >
> > > Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
> > > ---
> > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > > index aa51756..85c4d3f 100644
> > > --- a/drivers/clk/clk.c
> > > +++ b/drivers/clk/clk.c
> > > @@ -3435,6 +3435,7 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
> > > if (!dst)
> > > return -ENOMEM;
> > >
> > > + kfree_const(dst);
> > So you are now returning a freed pointer in dst_p?
> Thanks for your reply. I re-examined the code, and this kfree is
> incorrect and it should be deleted.
> > > return 0;
> > > }
> > >
> > > @@ -3491,6 +3492,8 @@ static int clk_core_populate_parent_map(struct clk_core *core)
> > > kfree_const(parents[i].name);
> > > kfree_const(parents[i].fw_name);
> > > } while (--i >= 0);
> > > + kfree_const(parent->name);
> > > + kfree_const(parent->fw_name);
> > Both of them were just freed in the loop above, no?
> for (i = 0, parent = parents; i < num_parents; i++, parent++)
> Is 'parent' the same as the one from the loop above?
Yes. Did it change somehow?
> Moreover, should 'parents[i].name' and 'parents[i].fw_name' be freed by
Yes? They're allocated with kstrdup_const() in clk_cpy_name(), or
they're NULL by virtue of the kcalloc and then kfree_const() does
I'm having a hard time following what this patch is trying to fix. It
looks unnecessary though so I'm going to drop it from the clk review