Nouveau - May 2022 - [PATCH v3] drm/nouveau: clear output poll workers before nouveau_fbcon_destroy()

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 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: dri-devel at lists.freedesktop.org
Cc: nouveau at lists.freedesktop.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Mark Menzynski <mmenzyns at 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 at 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 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: dri-devel at lists.freedesktop.org
> Cc: nouveau at lists.freedesktop.org
> Cc: linux-kernel at vger.kernel.org
> Signed-off-by: Mark Menzynski <mmenzyns at 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