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    Subject[PATCH 4.14 38/79] drm/meson: fix shutdown crash when component not probed
    Date
    From: Neil Armstrong <narmstrong@baylibre.com>

    commit 7cfc4ea78fc103ea51ecbacd9236abb5b1c490d2 upstream.

    When main component is not probed, by example when the dw-hdmi module is
    not loaded yet or in probe defer, the following crash appears on shutdown:

    Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038
    ...
    pc : meson_drv_shutdown+0x24/0x50
    lr : platform_drv_shutdown+0x20/0x30
    ...
    Call trace:
    meson_drv_shutdown+0x24/0x50
    platform_drv_shutdown+0x20/0x30
    device_shutdown+0x158/0x360
    kernel_restart_prepare+0x38/0x48
    kernel_restart+0x18/0x68
    __do_sys_reboot+0x224/0x250
    __arm64_sys_reboot+0x24/0x30
    ...

    Simply check if the priv struct has been allocated before using it.

    Fixes: fa0c16caf3d7 ("drm: meson_drv add shutdown function")
    Reported-by: Stefan Agner <stefan@agner.ch>
    Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
    Tested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
    Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20210430082744.3638743-1-narmstrong@baylibre.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/meson/meson_drv.c | 9 +++++----
    1 file changed, 5 insertions(+), 4 deletions(-)

    --- a/drivers/gpu/drm/meson/meson_drv.c
    +++ b/drivers/gpu/drm/meson/meson_drv.c
    @@ -364,11 +364,12 @@ static int meson_probe_remote(struct pla
    static void meson_drv_shutdown(struct platform_device *pdev)
    {
    struct meson_drm *priv = dev_get_drvdata(&pdev->dev);
    - struct drm_device *drm = priv->drm;

    - DRM_DEBUG_DRIVER("\n");
    - drm_kms_helper_poll_fini(drm);
    - drm_atomic_helper_shutdown(drm);
    + if (!priv)
    + return;
    +
    + drm_kms_helper_poll_fini(priv->drm);
    + drm_atomic_helper_shutdown(priv->drm);
    }

    static int meson_drv_probe(struct platform_device *pdev)

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