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.

This patch introduces another output poll clearing before fbcon
resources are destroyed.

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

Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Karol Herbst <kherbst@redhat.com>
Cc: Lyude Paul <lyude@redhat.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Mark Menzynski <mmenzyns@redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_fbcon.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index 4f9b3aa5deda..5226323e55d3 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -39,6 +39,7 @@
 
 #include <drm/drm_crtc.h>
 #include <drm/drm_crtc_helper.h>
+#include <drm/drm_probe_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_atomic.h>
@@ -605,6 +606,7 @@ nouveau_fbcon_fini(struct drm_device *dev)
 	if (!drm->fbcon)
 		return;
 
+	drm_kms_helper_poll_fini(dev);
 	nouveau_fbcon_accel_fini(dev);
 	nouveau_fbcon_destroy(dev, drm->fbcon);
 	kfree(drm->fbcon);
-- 
2.32.0

Reviewed-by: Lyude Paul <lyude@redhat.com>

Will push to the appropriate branch in a bit, thanks!

On Mon, 2022-05-23 at 13:35 +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.
> 
> This patch introduces another output poll clearing before fbcon
> resources are destroyed.
> 
> BUG: KASAN: use-after-free in
> __drm_fb_helper_initial_config_and_unlock.cold+0x1f3/0x291
> [drm_kms_helper]
> 
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: Karol Herbst <kherbst@redhat.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org
> Cc: nouveau@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Mark Menzynski <mmenzyns@redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_fbcon.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
> b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
> index 4f9b3aa5deda..5226323e55d3 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
> @@ -39,6 +39,7 @@
>  
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_crtc_helper.h>
> +#include <drm/drm_probe_helper.h>
>  #include <drm/drm_fb_helper.h>
>  #include <drm/drm_fourcc.h>
>  #include <drm/drm_atomic.h>
> @@ -605,6 +606,7 @@ nouveau_fbcon_fini(struct drm_device *dev)
>         if (!drm->fbcon)
>                 return;
>  
> +       drm_kms_helper_poll_fini(dev);
>         nouveau_fbcon_accel_fini(dev);
>         nouveau_fbcon_destroy(dev, drm->fbcon);
>         kfree(drm->fbcon);

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat