On Wed, Nov 18, 2015 at 01:43:20PM +0100, Lukas Wunner wrote:
> intelfb_create() is called once on driver initialization. If it fails,
> ifbdev->helper.fbdev, ifbdev->fb or ifbdev->fb->obj may be NULL.
>
> Further up in the call stack, intel_fbdev_initial_config() calls
> intel_fbdev_fini() to tear down the ifbdev on failure. This calls
> intel_fbdev_destroy() which dereferences ifbdev->fb. Fix the ensuing
> oops.
>
> Also check in these functions if ifbdev is not NULL to avoid oops:
>
> i915_gem_framebuffer_info() is called on access to debugfs file
> "i915_gem_framebuffer" and dereferences ifbdev, ifbdev->helper.fb
> and ifbdev->helper.fb->obj.
>
> intel_connector_add_to_fbdev() / intel_connector_remove_from_fbdev()
> are called when registering / unregistering an mst connector and
> dereference ifbdev.
>
> v3: Drop additional null pointer checks in intel_fbdev_set_suspend(),
> intel_fbdev_output_poll_changed() and intel_fbdev_restore_mode()
> since they already check if ifbdev is not NULL, which is sufficient
> now that intel_fbdev_fini() is called on initialization failure.
> (Requested by Daniel Vetter <daniel.vetter@xxxxxxxx>)
>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Queued for -next, thanks for the patch. Aside, with this patch and the
static inline dummies from Archit I think we can drop most of the #ifdef
blocks (not the one in debugfs though). Care for a follow-up patch to
remove them around add/remove_one_connector?
-Daniel
> ---
> drivers/gpu/drm/i915/i915_debugfs.c | 24 +++++++++++++-----------
> drivers/gpu/drm/i915/intel_dp_mst.c | 10 ++++++++--
> drivers/gpu/drm/i915/intel_fbdev.c | 6 ++++--
> 3 files changed, 25 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 038d5c6..411a9c6 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -1877,17 +1877,19 @@ static int i915_gem_framebuffer_info(struct seq_file *m, void *data)
> struct drm_i915_private *dev_priv = dev->dev_private;
>
> ifbdev = dev_priv->fbdev;
> - fb = to_intel_framebuffer(ifbdev->helper.fb);
> -
> - seq_printf(m, "fbcon size: %d x %d, depth %d, %d bpp, modifier 0x%llx, refcount %d, obj ",
> - fb->base.width,
> - fb->base.height,
> - fb->base.depth,
> - fb->base.bits_per_pixel,
> - fb->base.modifier[0],
> - atomic_read(&fb->base.refcount.refcount));
> - describe_obj(m, fb->obj);
> - seq_putc(m, '\n');
> + if (ifbdev) {
> + fb = to_intel_framebuffer(ifbdev->helper.fb);
> +
> + seq_printf(m, "fbcon size: %d x %d, depth %d, %d bpp, modifier 0x%llx, refcount %d, obj ",
> + fb->base.width,
> + fb->base.height,
> + fb->base.depth,
> + fb->base.bits_per_pixel,
> + fb->base.modifier[0],
> + atomic_read(&fb->base.refcount.refcount));
> + describe_obj(m, fb->obj);
> + seq_putc(m, '\n');
> + }
> #endif
>
> mutex_lock(&dev->mode_config.fb_lock);
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index 9d8a5b4..8c4e7df 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -408,7 +408,10 @@ static void intel_connector_add_to_fbdev(struct intel_connector *connector)
> {
> #ifdef CONFIG_DRM_FBDEV_EMULATION
> struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> - drm_fb_helper_add_one_connector(&dev_priv->fbdev->helper, &connector->base);
> +
> + if (dev_priv->fbdev)
> + drm_fb_helper_add_one_connector(&dev_priv->fbdev->helper,
> + &connector->base);
> #endif
> }
>
> @@ -416,7 +419,10 @@ static void intel_connector_remove_from_fbdev(struct intel_connector *connector)
> {
> #ifdef CONFIG_DRM_FBDEV_EMULATION
> struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> - drm_fb_helper_remove_one_connector(&dev_priv->fbdev->helper, &connector->base);
> +
> + if (dev_priv->fbdev)
> + drm_fb_helper_remove_one_connector(&dev_priv->fbdev->helper,
> + &connector->base);
> #endif
> }
>
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index cd345c5..7ccde58 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -530,8 +530,10 @@ static void intel_fbdev_destroy(struct drm_device *dev,
>
> drm_fb_helper_fini(&ifbdev->helper);
>
> - drm_framebuffer_unregister_private(&ifbdev->fb->base);
> - drm_framebuffer_remove(&ifbdev->fb->base);
> + if (ifbdev->fb) {
> + drm_framebuffer_unregister_private(&ifbdev->fb->base);
> + drm_framebuffer_remove(&ifbdev->fb->base);
> + }
> }
>
> /*
> --
> 2.1.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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