From: Ville Syrjälä ville.syrjala@linux.intel.com
struct drm_display_mode embeds a list head, so overwriting the full struct with another one will corrupt the list (if the destination mode is on a list). Use drm_mode_copy() instead which explicitly preserves the list head of the destination mode.
Even if we know the destination mode is not on any list using drm_mode_copy() seems decent as it sets a good example. Bad examples of not using it might eventually get copied into code where preserving the list head actually matters.
Obviously one case not covered here is when the mode itself is embedded in a larger structure and the whole structure is copied. But if we are careful when copying into modes embedded in structures I think we can be a little more reassured that bogus list heads haven't been propagated in.
@is_mode_copy@ @@ drm_mode_copy(...) { ... }
@depends on !is_mode_copy@ struct drm_display_mode *mode; expression E, S; @@ ( - *mode = E + drm_mode_copy(mode, &E) | - memcpy(mode, E, S) + drm_mode_copy(mode, E) )
@depends on !is_mode_copy@ struct drm_display_mode mode; expression E; @@ ( - mode = E + drm_mode_copy(&mode, &E) | - memcpy(&mode, E, S) + drm_mode_copy(&mode, E) )
@@ struct drm_display_mode *mode; @@ - &*mode + mode
Cc: Emma Anholt emma@anholt.net Cc: Maxime Ripard mripard@kernel.org Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com --- drivers/gpu/drm/vc4/vc4_hdmi.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index 5ac3216f2d4a..6c58b0fd13fb 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -1234,9 +1234,8 @@ static void vc4_hdmi_encoder_atomic_mode_set(struct drm_encoder *encoder, struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
mutex_lock(&vc4_hdmi->mutex); - memcpy(&vc4_hdmi->saved_adjusted_mode, - &crtc_state->adjusted_mode, - sizeof(vc4_hdmi->saved_adjusted_mode)); + drm_mode_copy(&vc4_hdmi->saved_adjusted_mode, + &crtc_state->adjusted_mode); mutex_unlock(&vc4_hdmi->mutex); }