Nouveau - May 2022 - [PATCH] drm/nouveau: reorder nouveau_drm_device_fini

Resources needed for output poll workers are destroyed in
nouveau_fbcon_fini() before output poll workers are cleared in
nouveau_display_fini(). This means there is a time between fbcon_fini
and display_fini, where if output poll happens, it crashes.

BUG: KASAN: use-after-free in
__drm_fb_helper_initial_config_and_unlock.cold+0x1f3/0x291
[drm_kms_helper]

Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: Karol Herbst <kherbst at redhat.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Sumit Semwal <sumit.semwal at linaro.org>
Cc: "Christian K?nig" <christian.koenig at amd.com>
Cc: dri-devel at lists.freedesktop.org
Cc: nouveau at lists.freedesktop.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-media at vger.kernel.org
Cc: linaro-mm-sig at lists.linaro.org
Signed-off-by: Mark Menzynski <mmenzyns at redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_drm.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c
b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 561309d447e0..773efdd20d2f 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -588,12 +588,6 @@ nouveau_drm_device_init(struct drm_device *dev)
 	if (ret)
 		goto fail_dispctor;
 
-	if (dev->mode_config.num_crtc) {
-		ret = nouveau_display_init(dev, false, false);
-		if (ret)
-			goto fail_dispinit;
-	}
-
 	nouveau_debugfs_init(drm);
 	nouveau_hwmon_init(dev);
 	nouveau_svm_init(drm);
@@ -601,6 +595,12 @@ nouveau_drm_device_init(struct drm_device *dev)
 	nouveau_fbcon_init(dev);
 	nouveau_led_init(dev);
 
+	if (dev->mode_config.num_crtc) {
+		ret = nouveau_display_init(dev, false, false);
+		if (ret)
+			goto fail_dispinit;
+	}
+
 	if (nouveau_pmops_runtime()) {
 		pm_runtime_use_autosuspend(dev->dev);
 		pm_runtime_set_autosuspend_delay(dev->dev, 5000);
@@ -641,15 +641,14 @@ nouveau_drm_device_fini(struct drm_device *dev)
 		pm_runtime_forbid(dev->dev);
 	}
 
+	if (dev->mode_config.num_crtc)
+		nouveau_display_fini(dev, false, false);
 	nouveau_led_fini(dev);
 	nouveau_fbcon_fini(dev);
 	nouveau_dmem_fini(drm);
 	nouveau_svm_fini(drm);
 	nouveau_hwmon_fini(dev);
 	nouveau_debugfs_fini(drm);
-
-	if (dev->mode_config.num_crtc)
-		nouveau_display_fini(dev, false, false);
 	nouveau_display_destroy(dev);
 
 	nouveau_accel_fini(drm);
-- 
2.32.0

Hmm, I think we might just need to move the drm_kms_helper_poll_enable() call
to the end here instead of all of nouveau_display_init(). I realized this
because in nouveau_display_init() it seems that we actually rely on
nouveau_display_init() to setup hotplug interrupts - which we do actually need
this early on in the driver probe process.

That being said though, drm_kms_helper_poll_enable() shouldn't be required
for
MST short HPD IRQs from working so moving that instead should work.

On Wed, 2022-05-04 at 19:18 +0200, Mark Menzynski wrote:
> Resources needed for output poll workers are destroyed in
> nouveau_fbcon_fini() before output poll workers are cleared in
> nouveau_display_fini(). This means there is a time between fbcon_fini
> and display_fini, where if output poll happens, it crashes.
> 
> BUG: KASAN: use-after-free in
> __drm_fb_helper_initial_config_and_unlock.cold+0x1f3/0x291
> [drm_kms_helper]
> 
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: "Christian K?nig" <christian.koenig at amd.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: nouveau at lists.freedesktop.org
> Cc: linux-kernel at vger.kernel.org
> Cc: linux-media at vger.kernel.org
> Cc: linaro-mm-sig at lists.linaro.org
> Signed-off-by: Mark Menzynski <mmenzyns at redhat.com>
> ---
> ?drivers/gpu/drm/nouveau/nouveau_drm.c | 17 ++++++++---------
> ?1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c
> b/drivers/gpu/drm/nouveau/nouveau_drm.c
> index 561309d447e0..773efdd20d2f 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> @@ -588,12 +588,6 @@ nouveau_drm_device_init(struct drm_device *dev)
> ????????if (ret)
> ????????????????goto fail_dispctor;
> ?
> -???????if (dev->mode_config.num_crtc) {
> -???????????????ret = nouveau_display_init(dev, false, false);
> -???????????????if (ret)
> -???????????????????????goto fail_dispinit;
> -???????}
> -
> ????????nouveau_debugfs_init(drm);
> ????????nouveau_hwmon_init(dev);
> ????????nouveau_svm_init(drm);
> @@ -601,6 +595,12 @@ nouveau_drm_device_init(struct drm_device *dev)
> ????????nouveau_fbcon_init(dev);
> ????????nouveau_led_init(dev);
> ?
> +???????if (dev->mode_config.num_crtc) {
> +???????????????ret = nouveau_display_init(dev, false, false);
> +???????????????if (ret)
> +???????????????????????goto fail_dispinit;
> +???????}
> +
> ????????if (nouveau_pmops_runtime()) {
> ????????????????pm_runtime_use_autosuspend(dev->dev);
> ????????????????pm_runtime_set_autosuspend_delay(dev->dev, 5000);
> @@ -641,15 +641,14 @@ nouveau_drm_device_fini(struct drm_device *dev)
> ????????????????pm_runtime_forbid(dev->dev);
> ????????}
> ?
> +???????if (dev->mode_config.num_crtc)
> +???????????????nouveau_display_fini(dev, false, false);
> ????????nouveau_led_fini(dev);
> ????????nouveau_fbcon_fini(dev);
> ????????nouveau_dmem_fini(drm);
> ????????nouveau_svm_fini(drm);
> ????????nouveau_hwmon_fini(dev);
> ????????nouveau_debugfs_fini(drm);
> -
> -???????if (dev->mode_config.num_crtc)
> -???????????????nouveau_display_fini(dev, false, false);
> ????????nouveau_display_destroy(dev);
> ?
> ????????nouveau_accel_fini(drm);
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat