From 6808abdb33bf90330e70a687d29f038507e06ebb Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan+linaro@kernel.org>
Date: Tue, 13 Sep 2022 10:53:11 +0200
Subject: [PATCH] drm/msm: fix use-after-free on probe deferral
Git-commit: 6808abdb33bf90330e70a687d29f038507e06ebb
Patch-mainline: v6.1-rc3
References: git-fixes

The bridge counter was never reset when tearing down the DRM device so
that stale pointers to deallocated structures would be accessed on the
next tear down (e.g. after a second late bind deferral).

Given enough bridges and a few probe deferrals this could currently also
lead to data beyond the bridge array being corrupted.

Fixes: d28ea556267c ("drm/msm: properly add and remove internal bridges")
Fixes: a3376e3ec81c ("drm/msm: convert to drm_bridge")
Cc: stable@vger.kernel.org      # 3.12
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/502665/
Link: https://lore.kernel.org/r/20220913085320.8577-2-johan+linaro@kernel.org
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/msm/msm_drv.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -296,6 +296,7 @@ static int msm_drm_uninit(struct device
 
 	for (i = 0; i < priv->num_bridges; i++)
 		drm_bridge_remove(priv->bridges[i]);
+	priv->num_bridges = 0;
 
 	pm_runtime_get_sync(dev);
 	drm_irq_uninstall(ddev);