linux-kernel - [PATCH] drm/prime: Ensure mmap offset is initialized

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Date:   Sun, 29 May 2022 09:29:36 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Gerd Hoffmann <kraxel@...hat.com>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] drm/prime: Ensure mmap offset is initialized

From: Rob Clark <robdclark@...omium.org>

If a GEM object is allocated, and then exported as a dma-buf fd which is
mmap'd before or without the GEM buffer being directly mmap'd, the
vma_node could be unitialized.  This leads to a situation where the CPU
mapping is not correctly torn down in drm_vma_node_unmap().

Fixes: e5516553999f ("drm: call drm_gem_object_funcs.mmap with fake offset")
Signed-off-by: Rob Clark <robdclark@...omium.org>
---
Note, it's possible the issue existed in some related form prior to the
commit tagged with Fixes.

 drivers/gpu/drm/drm_prime.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index e3f09f18110c..849eea154dfc 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -716,6 +716,11 @@ int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
 	struct file *fil;
 	int ret;
 
+	/* Ensure that the vma_node is initialized: */
+	ret = drm_gem_create_mmap_offset(obj);
+	if (ret)
+		return ret;
+
 	/* Add the fake offset */
 	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
 
-- 
2.35.3