Hi,
On 14/04/2022 09:14, Xiaomeng Tong wrote:
The bug is here:
bus_flags = connector->display_info.bus_flags;
The list iterator 'connector-' will point to a bogus position containing
HEAD if the list is empty or no element is found. This case must
be checked before any use of the iterator, otherwise it will lead
to a invalid memory access.
To fix this bug, add an check. Use a new value 'iter' as the list
iterator, while use the old value 'connector' as a dedicated variable
to point to the found element.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: ("drm/omap: Add support for drm_panel")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@xxxxxxxxx>
---
drivers/gpu/drm/omapdrm/omap_encoder.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c
index 4dd05bc732da..d648ab4223b1 100644
--- a/drivers/gpu/drm/omapdrm/omap_encoder.c
+++ b/drivers/gpu/drm/omapdrm/omap_encoder.c
@@ -76,14 +76,16 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder,
struct omap_encoder *omap_encoder = to_omap_encoder(encoder);
struct omap_dss_device *output = omap_encoder->output;
struct drm_device *dev = encoder->dev;
- struct drm_connector *connector;
+ struct drm_connector *connector = NULL, *iter;
struct drm_bridge *bridge;
struct videomode vm = { 0 };
u32 bus_flags;
- list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
- if (connector->encoder == encoder)
+ list_for_each_entry(iter, &dev->mode_config.connector_list, head) {
+ if (iter->encoder == encoder) {
+ connector = iter;
break;
+ }
}
When does this bug happen? How do you get omap_encoder_mode_set() called
for an encoder with a connector that is not valid?
drm_display_mode_to_videomode(adjusted_mode, &vm);
@@ -106,8 +108,10 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder,
omap_encoder_update_videomode_flags(&vm, bus_flags);
}
- bus_flags = connector->display_info.bus_flags;
- omap_encoder_update_videomode_flags(&vm, bus_flags);
+ if (connector) {
+ bus_flags = connector->display_info.bus_flags;
+ omap_encoder_update_videomode_flags(&vm, bus_flags);
+ }
/* Set timings for all devices in the display pipeline. */
dss_mgr_set_timings(output, &vm);
How does this fix the issue? You just skip the lines that set up the
videomode, but then pass that videomode to dss_mgr_set_timings()...
Tomi
