Re: Re: [PATCH] drm/nouveau/clk/gm20b: Fix memory leak in gm20b_clk_new

From: Ben Skeggs
Date: Sun May 31 2020 - 23:37:38 EST

On Mon, 1 Jun 2020 at 13:27, <dinghao.liu@xxxxxxxxxx> wrote:
> Hi Ben,
> > > When gk20a_clk_ctor() returns an error code, pointer "clk"
> > > should be released. It's the same when gm20b_clk_new()
> > > returns from elsewhere following this call.
> > This shouldn't be necessary. If a subdev constructor fails, and
> > returns a pointer, the core will call the destructor to clean things
> > up.
> >
> I'm not familiar with the behavior of the caller of gm20b_clk_new().
> If the subdev constructor fails, the core will check the pointer
> (here is "pclk"), then it's ok and there is no bug (Do you mean
> this?). If the core executes error handling code only according to
> the error code, there may be a memory leak bug (the caller cannot
> know if -ENOMEM comes from the failure of kzalloc or gk20a_clk_ctor).
> If the core always calls the destructor as long as the constructor
> fails (even if the kzalloc fails), we may have a double free bug.
> Would you like to give a more detailed explanation about the behavior
> of the core?
If there's *any* error, it'll check the pointer, if it's non-NULL,
it'll call the destructor. If kzalloc() fails, the pointer will be
NULL, there's no double-free bug. *every* subdev is written this way
to avoid duplicating cleanup logic.

> Regards,
> Dinghao