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    Subject[PATCH 4.14 17/41] drm/nouveau/bl: Fix oops on driver unbind
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Lukas Wunner <lukas@wunner.de>

    commit 76f2e2bc627f7d08360ac731b6277d744d4eb599 upstream.

    Unbinding nouveau on a dual GPU MacBook Pro oopses because we iterate
    over the bl_connectors list in nouveau_backlight_exit() but skipped
    initializing it in nouveau_backlight_init(). Stacktrace for posterity:

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
    IP: nouveau_backlight_exit+0x2b/0x70 [nouveau]
    nouveau_display_destroy+0x29/0x80 [nouveau]
    nouveau_drm_unload+0x65/0xe0 [nouveau]
    drm_dev_unregister+0x3c/0xe0 [drm]
    drm_put_dev+0x2e/0x60 [drm]
    nouveau_drm_device_remove+0x47/0x70 [nouveau]
    pci_device_remove+0x36/0xb0
    device_release_driver_internal+0x157/0x220
    driver_detach+0x39/0x70
    bus_remove_driver+0x51/0xd0
    pci_unregister_driver+0x2a/0xa0
    nouveau_drm_exit+0x15/0xfb0 [nouveau]
    SyS_delete_module+0x18c/0x290
    system_call_fast_compare_end+0xc/0x6f

    Fixes: b53ac1ee12a3 ("drm/nouveau/bl: Do not register interface if Apple GMUX detected")
    Cc: stable@vger.kernel.org # v4.10+
    Cc: Pierre Moreau <pierre.morrow@free.fr>
    Signed-off-by: Lukas Wunner <lukas@wunner.de>
    Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

    --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
    +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
    @@ -268,13 +268,13 @@ nouveau_backlight_init(struct drm_device
    struct nvif_device *device = &drm->client.device;
    struct drm_connector *connector;

    + INIT_LIST_HEAD(&drm->bl_connectors);
    +
    if (apple_gmux_present()) {
    NV_INFO(drm, "Apple GMUX detected: not registering Nouveau backlight interface\n");
    return 0;
    }

    - INIT_LIST_HEAD(&drm->bl_connectors);
    -
    list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
    if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS &&
    connector->connector_type != DRM_MODE_CONNECTOR_eDP)

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