From: Daniel Vetter <daniel@ffwll.ch>
To: Julia Lawall <Julia.Lawall@inria.fr>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
kernel-janitors@vger.kernel.org,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/of: free the right object
Date: Mon, 12 Jul 2021 16:25:41 +0200 [thread overview]
Message-ID: <YOxQ5TbkNrqCGBDJ@phenom.ffwll.local> (raw)
In-Reply-To: <20210709200717.3676376-1-Julia.Lawall@inria.fr>
On Fri, Jul 09, 2021 at 10:07:17PM +0200, Julia Lawall wrote:
> There is no need to free a NULL value. Instead, free the object
> that is leaking due to the iterator.
>
> The semantic patch that finds this problem is as follows:
>
> // <smpl>
> @@
> expression x,e;
> identifier f;
> @@
> x = f(...);
> if (x == NULL) {
> ... when any
> when != x = e
> * of_node_put(x);
> ...
> }
> // </smpl>
>
> Fixes: 6529007522de ("drm: of: Add drm_of_lvds_get_dual_link_pixel_order")
> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Applied to drm-misc-next, thanks for your patch.
Random rant about this for_each_child_of_node():
- not documented with kerneldoc
- very dangerous since the seemingly correct usage leaks
What we've done here for similar refcounted iterators is a 3 step process:
- iter_init()
- for_each_iter() macro
- iter_fini(), which has to be always called after iter_init and cleans up
the last reference.
Then it's a lot more obvious that you call iter_fini() when you break out
of a loop. Trying to hide that in the for_each macro is a bit much.
Cheers, Daniel
>
> ---
> drivers/gpu/drm/drm_of.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index ca04c34e8251..197c57477344 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -315,7 +315,7 @@ static int drm_of_lvds_get_remote_pixels_type(
>
> remote_port = of_graph_get_remote_port(endpoint);
> if (!remote_port) {
> - of_node_put(remote_port);
> + of_node_put(endpoint);
> return -EPIPE;
> }
>
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
WARNING: multiple messages have this Message-ID (diff)
From: Daniel Vetter <daniel@ffwll.ch>
To: Julia Lawall <Julia.Lawall@inria.fr>
Cc: Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>,
kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/of: free the right object
Date: Mon, 12 Jul 2021 16:25:41 +0200 [thread overview]
Message-ID: <YOxQ5TbkNrqCGBDJ@phenom.ffwll.local> (raw)
In-Reply-To: <20210709200717.3676376-1-Julia.Lawall@inria.fr>
On Fri, Jul 09, 2021 at 10:07:17PM +0200, Julia Lawall wrote:
> There is no need to free a NULL value. Instead, free the object
> that is leaking due to the iterator.
>
> The semantic patch that finds this problem is as follows:
>
> // <smpl>
> @@
> expression x,e;
> identifier f;
> @@
> x = f(...);
> if (x == NULL) {
> ... when any
> when != x = e
> * of_node_put(x);
> ...
> }
> // </smpl>
>
> Fixes: 6529007522de ("drm: of: Add drm_of_lvds_get_dual_link_pixel_order")
> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Applied to drm-misc-next, thanks for your patch.
Random rant about this for_each_child_of_node():
- not documented with kerneldoc
- very dangerous since the seemingly correct usage leaks
What we've done here for similar refcounted iterators is a 3 step process:
- iter_init()
- for_each_iter() macro
- iter_fini(), which has to be always called after iter_init and cleans up
the last reference.
Then it's a lot more obvious that you call iter_fini() when you break out
of a loop. Trying to hide that in the for_each macro is a bit much.
Cheers, Daniel
>
> ---
> drivers/gpu/drm/drm_of.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index ca04c34e8251..197c57477344 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -315,7 +315,7 @@ static int drm_of_lvds_get_remote_pixels_type(
>
> remote_port = of_graph_get_remote_port(endpoint);
> if (!remote_port) {
> - of_node_put(remote_port);
> + of_node_put(endpoint);
> return -EPIPE;
> }
>
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2021-07-12 14:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 20:07 [PATCH] drm/of: free the right object Julia Lawall
2021-07-09 20:07 ` Julia Lawall
2021-07-12 14:25 ` Daniel Vetter [this message]
2021-07-12 14:25 ` Daniel Vetter
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