[PATCH 5.10 68/95] drm: mxsfb: Fix NULL pointer dereference crash on unload

Greg Kroah-Hartman
2021-10-25T19:43:02Z

From: Marek Vasut <marex@denx.de>

commit 3cfc183052c3dbf8eae57b6c1685dab00ed3db4a upstream.

The mxsfb->crtc.funcs may already be NULL when unloading the driver,
in which case calling mxsfb_irq_disable() via drm_irq_uninstall() from
mxsfb_unload() leads to NULL pointer dereference.

Since all we care about is masking the IRQ and mxsfb->base is still
valid, just use that to clear and mask the IRQ.

Fixes: ae1ed00932819 ("drm: mxsfb: Stop using DRM simple display pipeline helper")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Abrecht <public@danielabrecht.ch>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Stefan Agner <stefan@agner.ch>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211016210446.171616-1-marex@denx.de
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/mxsfb/mxsfb_drv.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
@@ -268,7 +268,11 @@ static void mxsfb_irq_disable(struct drm
struct mxsfb_drm_private *mxsfb = drm->dev_private;

mxsfb_enable_axi_clk(mxsfb);
- mxsfb->crtc.funcs->disable_vblank(&mxsfb->crtc);
+
+ /* Disable and clear VBLANK IRQ */
+ writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1 + REG_CLR);
+ writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 + REG_CLR);
+
mxsfb_disable_axi_clk(mxsfb);
}