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Message-ID: <OS0PR01MB592294867B449F855496337186159@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date: Mon, 12 Jul 2021 16:03:55 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Steven Price <steven.price@....com>,
Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...ux.ie>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Pavel Machek <pavel@...x.de>
Subject: RE: [PATCH] drm/of: free the iterator object on failure
+ Pavel
> -----Original Message-----
> From: Steven Price <steven.price@....com>
> Sent: 12 July 2021 16:58
> To: Daniel Vetter <daniel@...ll.ch>; David Airlie <airlied@...ux.ie>;
> Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>; Maxime Ripard
> <mripard@...nel.org>; Thomas Zimmermann <tzimmermann@...e.de>
> Cc: Steven Price <steven.price@....com>; dri-devel@...ts.freedesktop.org;
> linux-kernel@...r.kernel.org; Biju Das <biju.das.jz@...renesas.com>;
> Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Subject: [PATCH] drm/of: free the iterator object on failure
>
> When bailing out due to the sanity check the iterator value needs to be
> freed because the early return prevents for_each_child_of_node() from
> doing the dereference itself.
>
> Fixes: 4ee48cc5586b ("drm: of: Fix double-free bug")
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> drivers/gpu/drm/drm_of.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> Daniel's email[1] made me take a look at this function and it appears that
> for_each_child_of_node()'s interface had caused a bad bug fix due to the
> hidden reference counting in the iterator.
>
> [1]
> https://jpn01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.ker
> nel.org%2Fr%2FYOxQ5TbkNrqCGBDJ%2540phenom.ffwll.local&data=04%7C01%7Cb
> iju.das.jz%40bp.renesas.com%7Cb0570b66e03a43fb8fa008d9454dddaa%7C53d82571d
> a1947e49cb4625a166a4a2a%7C0%7C0%7C637617023006562683%7CUnknown%7CTWFpbGZsb
> 3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C10
> 00&sdata=cQICPYJzmgNkFsNw1wMH9Or73rohnCCGH1DrUg3hvhw%3D&reserved=0
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c index
> 197c57477344..997b8827fed2 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -331,8 +331,10 @@ static int drm_of_lvds_get_remote_pixels_type(
> * configurations by passing the endpoints explicitly to
> * drm_of_lvds_get_dual_link_pixel_order().
> */
> - if (!current_pt || pixels_type != current_pt)
> + if (!current_pt || pixels_type != current_pt) {
> + of_node_put(endpoint);
> return -EINVAL;
> + }
> }
>
> return pixels_type;
> --
> 2.20.1
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