i915: intel_set_mode: Reduce stack allocation from 500 bytes to 2 pointers

smatch warning:

drivers/gpu/drm/i915/intel_display.c:7019 intel_set_mode() warn: function puts
500 bytes on stack

Refactor so that saved_mode and saved_hwmode are dynamically allocated as opposed
to being automatic variables. 500 bytes seems like it could run the potential for blowing
the kernel stack.

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 34832bc..115bf62 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7398,11 +7398,18 @@ bool intel_set_mode(struct drm_crtc *crtc,
 {
        struct drm_device *dev = crtc->dev;
        drm_i915_private_t *dev_priv = dev->dev_private;
-       struct drm_display_mode *adjusted_mode, saved_mode, saved_hwmode;
+       struct drm_display_mode *adjusted_mode, *saved_mode, *saved_hwmode;
        struct intel_crtc *intel_crtc;
        unsigned disable_pipes, prepare_pipes, modeset_pipes;
        bool ret = true;
 
+       saved_mode = kmalloc(2 * sizeof(*saved_mode), GFP_KERNEL);
+       if (!saved_mode) {
+               DRM_ERROR("i915: Could not allocate saved display mode.\n");
+               return false;
+       }
+       saved_hwmode = saved_mode + 1;
+
        intel_modeset_affected_pipes(crtc, &modeset_pipes,
                                     &prepare_pipes, &disable_pipes);
 
@@ -7412,8 +7419,8 @@ bool intel_set_mode(struct drm_crtc *crtc,
        for_each_intel_crtc_masked(dev, disable_pipes, intel_crtc)
                intel_crtc_disable(&intel_crtc->base);
 
-       saved_hwmode = crtc->hwmode;
-       saved_mode = crtc->mode;
+       *saved_hwmode = crtc->hwmode;
+       *saved_mode = crtc->mode;
 
        /* Hack: Because we don't (yet) support global modeset on multiple
         * crtcs, we don't keep track of the new mode for more than one crtc.
@@ -7424,7 +7431,8 @@ bool intel_set_mode(struct drm_crtc *crtc,
        if (modeset_pipes) {
                adjusted_mode = intel_modeset_adjusted_mode(crtc, mode);
                if (IS_ERR(adjusted_mode)) {
-                       return false;
+                       ret = false;
+                       goto out;
                }
        }
 
@@ -7476,12 +7484,14 @@ bool intel_set_mode(struct drm_crtc *crtc,
 done:
        drm_mode_destroy(dev, adjusted_mode);
        if (!ret && crtc->enabled) {
-               crtc->hwmode = saved_hwmode;
-               crtc->mode = saved_mode;
+               crtc->hwmode = *saved_hwmode;
+               crtc->mode = *saved_mode;
        } else {
                intel_modeset_check_state(dev);
        }
 
+out:
+       kfree(saved_mode);
        return ret;
 }