linux-kernel - [PATCH] drm/msm: correct NULL pointer dereference in context

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Date:   Wed, 26 Jun 2019 22:05:15 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     jcrouse@...eaurora.org, robdclark@...omium.org,
        seanpaul@...omium.org
Cc:     freedreno@...ts.freedesktop.org, jean-philippe.brucker@....com,
        linux-arm-msm@...r.kernel.org, hoegsberg@...gle.com,
        dianders@...omium.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, airlied@...ux.ie, daniel@...ll.ch
Subject: [PATCH] drm/msm: correct NULL pointer dereference in context_init

Correct attempted NULL pointer dereference in context_init() when
running without an IOMMU.

Signed-off-by: Brian Masney <masneyb@...tation.org>
Fixes: 295b22ae596c ("drm/msm: Pass the MMU domain index in struct msm_file_private")
---
The no IOMMU case seems like functionality that we may want to keep
based on this comment:
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/msm/adreno/a3xx_gpu.c#L523
Once I get the msm8974 interconnect driver done, I'm going to look into
what needs to be done to get the IOMMU working on the Nexus 5.

Alternatively, for development purposes, maybe we could have a NOOP
IOMMU driver that would allow us to remove these NULL checks that are
sprinkled throughout the code. I haven't looked into this in detail.
Thoughts?

 drivers/gpu/drm/msm/msm_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index 451bd4508793..83047cb2c735 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -619,7 +619,7 @@ static int context_init(struct drm_device *dev, struct drm_file *file)
 
 	msm_submitqueue_init(dev, ctx);
 
-	ctx->aspace = priv->gpu->aspace;
+	ctx->aspace = priv->gpu ? priv->gpu->aspace : NULL;
 	file->driver_priv = ctx;
 
 	return 0;
-- 
2.20.1