Messages in this thread | | | Subject | Re: [PATCH 1/1] drm/sun4i: hdmi: Check for null pointer before cleanup | From | Stefan Mavrodiev <> | Date | Tue, 17 Dec 2019 08:45:07 +0200 |
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Hi,
On 12/16/19 6:12 PM, Maxime Ripard wrote: > Hi, > > On Mon, Dec 16, 2019 at 04:43:48PM +0200, Stefan Mavrodiev wrote: >> It's possible hdmi->connector and hdmi->encoder divices to be NULL. >> This can happen when building as kernel module and you try to remove >> the module. >> >> This patch make simple null check, before calling the cleanup functions. >> >> Signed-off-by: Stefan Mavrodiev <stefan@olimex.com> >> --- >> drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c >> index a7c4654445c7..b61e00f2ecb8 100644 >> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c >> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c >> @@ -685,8 +685,10 @@ static void sun4i_hdmi_unbind(struct device *dev, struct device *master, >> struct sun4i_hdmi *hdmi = dev_get_drvdata(dev); >> >> cec_unregister_adapter(hdmi->cec_adap); >> - drm_connector_cleanup(&hdmi->connector); >> - drm_encoder_cleanup(&hdmi->encoder); >> + if (hdmi->connector.dev) >> + drm_connector_cleanup(&hdmi->connector); >> + if (hdmi->encoder.dev) >> + drm_encoder_cleanup(&hdmi->encoder); > Hmmm, this doesn't look right. Do you have more information on how you > can reproduce it?
Just build sun4i_drm_hdmi as module (CONFIG_DRM_SUN4I_HDMI=m). Then try to unload the module:
# rmmod sun4i_drm_hdmi
And you get this:
Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = 6b032436 [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: sun4i_drm_hdmi(-) CPU: 0 PID: 1081 Comm: rmmod Not tainted 5.5.0-rc1-00030-g6ec417030d93 #33 Hardware name: Allwinner sun7i (A20) Family PC is at drm_connector_cleanup+0x40/0x208 LR is at sun4i_hdmi_unbind+0x10/0x54 [sun4i_drm_hdmi] ...
I've tested that with sunxi/for-next branch on A20-OLinuXino board.
Best regards, Stefan
> > Maxime
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