drm: fix uninitialized acquire_ctx fields (v2)

robclark · danvet · commit c3e25ae34fab · 2014-06-18T13:50:25.000+02:00
The acquire ctx will typically be declared on the stack, which means we
could have garbage values for any uninitialized field.  In this case, it
was triggering WARN_ON()s because 'contended' had garbage value.

Go ahead and use memset() to be more future-proof.

v2: now with extra brown paper bag

Reported-by: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Signed-off-by: Rob Clark &lt;robdclark@gmail.com&gt;
Reviewed-by: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Tested-by: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Signed-off-by: Daniel Vetter &lt;daniel.vetter@ffwll.ch&gt;
diff --git a/drivers/gpu/drm/drm_modeset_lock.c b/drivers/gpu/drm/drm_modeset_lock.c
@@ -64,6 +64,7 @@
 void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,
 		uint32_t flags)
 {
+	memset(ctx, 0, sizeof(*ctx));
 	ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);
 	INIT_LIST_HEAD(&ctx->locked);
 }

Original file line number	Diff line number	Diff line change
`@@ -64,6 +64,7 @@`
`64`	`64`	`void drm_modeset_acquire_init(struct drm_modeset_acquire_ctx *ctx,`
`65`	`65`	`uint32_t flags)`
`66`	`66`	`{`
	`67`	`+ memset(ctx, 0, sizeof(*ctx));`
`67`	`68`	`ww_acquire_init(&ctx->ww_ctx, &crtc_ww_class);`
`68`	`69`	`INIT_LIST_HEAD(&ctx->locked);`
`69`	`70`	`}`