[PATCH v2 4/5] drm/panel: find_panel_by_fwnode() return a counted reference
Albert Esteve <[email protected]>
| Newsgroups | org.kernel.vger.linux-renesas-soc,dev.linux.lists.imx,dev.linux.lists.linux-sunxi,org.freedesktop.lists.dri-devel,org.infradead.lists.linux-rockchip,org.kernel.vger.linux-kernel,org.kernel.vger.linux-mips,org.kernel.vger.linux-samsung-soc,org.kernel.vger.linux-tegra |
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| Message-ID | <[email protected]> |
find_panel_by_fwnode() is the fwnode-based counterpart to of_drm_find_panel(), used internally by drm_panel_add_follower(). Like of_drm_find_panel(), it returned an unrefcounted pointer, leaving a window where the panel could be freed between the lookup and first use. drm_panel_add_follower() worked around the missing panel kref by calling get_device() on the panel's underlying struct device. However, get_device() only prevents the device kobject from being freed. It does not prevent the panel's kzalloc()'d container memory from being released when the kref reaches zero. Apply the same fix: call drm_panel_get() under panel_lock before returning. Since find_panel_by_fwnode() now transfers a counted reference to drm_panel_add_follower(), drm_panel_remove_follower() must balance it with a matching drm_panel_put(). Signed-off-by: Albert Esteve <[email protected]> --- drivers/gpu/drm/drm_panel.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c index 72cf86253c0cd..a00ae98ed0956 100644 --- a/drivers/gpu/drm/drm_panel.c +++ b/drivers/gpu/drm/drm_panel.c @@ -542,7 +542,13 @@ int of_drm_get_panel_orientation(const struct device_node *np, EXPORT_SYMBOL(of_drm_get_panel_orientation); #endif -/* Find panel by fwnode. This should be identical to of_drm_find_panel(). */ +/* + * Find panel by fwnode, returning a counted reference. + * + * Behaves identically to of_drm_find_panel(). On success the returned + * pointer has been passed through drm_panel_get(); the caller must call + * drm_panel_put() when done with it. + */ static struct drm_panel *find_panel_by_fwnode(const struct fwnode_handle *fwnode) { struct drm_panel *panel; @@ -554,6 +560,7 @@ static struct drm_panel *find_panel_by_fwnode(const struct fwnode_handle *fwnode list_for_each_entry(panel, &panel_list, list) { if (dev_fwnode(panel->dev) == fwnode) { + drm_panel_get(panel); mutex_unlock(&panel_lock); return panel; } @@ -690,6 +697,7 @@ void drm_panel_remove_follower(struct drm_panel_follower *follower) mutex_unlock(&panel->follower_lock); put_device(panel->dev); + drm_panel_put(panel); } EXPORT_SYMBOL(drm_panel_remove_follower); -- 2.54.0