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[17/22] drm/vc4: Use drm_mode_copy()

Message ID 20220218100403.7028-18-ville.syrjala@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series drm: Review of mode copies | expand

Commit Message

Ville Syrjälä Feb. 18, 2022, 10:03 a.m. UTC 
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(-)

Comments

Maxime Ripard Feb. 21, 2022, 10:13 a.m. UTC | #1 
On Fri, 18 Feb 2022 12:03:58 +0200, Ville Syrjala wrote:
> 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.
> 
> [...]

Applied to drm/drm-misc (drm-misc-next).

Thanks!
Maxime
diff mbox series

Patch

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);
 }