meson_drv_unbind() doesn't unregister the IRQ handler, which can lead to use-after-free if the IRQ fires after unbind:

[ 64.656876] Unable to handle kernel paging request at virtual address ffff000011706dbc ... [ 64.662001] pc : meson_irq+0x18/0x30 [meson_drm]

I'm assuming that a similar problem could happen on the error path of bind(), so uninstall the IRQ handler there as well.

Fixes: bbbe775ec5b5 ("drm: Add support for Amlogic Meson Graphic Controller") Signed-off-by: Jean-Philippe Brucker jean-philippe.brucker@arm.com --- drivers/gpu/drm/meson/meson_drv.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c index 7e85802c5398..8a4ebcb6405c 100644 --- a/drivers/gpu/drm/meson/meson_drv.c +++ b/drivers/gpu/drm/meson/meson_drv.c @@ -337,12 +337,14 @@ static int meson_drv_bind_master(struct device *dev, bool has_components)

ret = drm_dev_register(drm, 0); if (ret) - goto free_drm; + goto uninstall_irq;

drm_fbdev_generic_setup(drm, 32);

return 0;

+uninstall_irq: + drm_irq_uninstall(drm); free_drm: drm_dev_put(drm);

@@ -367,6 +369,7 @@ static void meson_drv_unbind(struct device *dev) }

drm_dev_unregister(drm); + drm_irq_uninstall(drm); drm_kms_helper_poll_fini(drm); drm_mode_config_cleanup(drm); drm_dev_put(drm);

Hi Jean-Philippe,

Le 22/03/2019 16:26, Jean-Philippe Brucker a écrit :

meson_drv_bind() registers a meson_drm struct as the device's privdata, but meson_drv_unbind() tries to retrieve a drm_device. This may cause a segfault on shutdown:

[ 5194.593429] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000197 ... [ 5194.788850] Call trace: [ 5194.791349] drm_dev_unregister+0x1c/0x118 [drm] [ 5194.795848] meson_drv_unbind+0x50/0x78 [meson_drm]

Retrieve the right pointer in meson_drv_unbind().

Fixes: bbbe775ec5b5 ("drm: Add support for Amlogic Meson Graphic Controller") Signed-off-by: Jean-Philippe Brucker jean-philippe.brucker@arm.com

Thanks for working on this, Acked-by: Neil Armstrong narmstrong@baylibre.com

I'll push it on drm-misc-fixes

---

drivers/gpu/drm/meson/meson_drv.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c index 2281ed3eb774..7e85802c5398 100644 --- a/drivers/gpu/drm/meson/meson_drv.c +++ b/drivers/gpu/drm/meson/meson_drv.c @@ -356,8 +356,8 @@ static int meson_drv_bind(struct device *dev)

static void meson_drv_unbind(struct device *dev) {

• struct drm_device *drm = dev_get_drvdata(dev);
• struct meson_drm *priv = drm->dev_private;

• struct meson_drm *priv = dev_get_drvdata(dev);

• struct drm_device *drm = priv->drm;

  if (priv->canvas) { meson_canvas_free(priv->canvas, priv->canvas_id_osd1);