[PATCH] drm/of: free the iterator object on failure

From: Steven Price
Date: Mon Jul 12 2021 - 11:58:22 EST


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@xxxxxxx>
---
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://lore.kernel.org/r/YOxQ5TbkNrqCGBDJ%40phenom.ffwll.local

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