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Revert "drm/gem-framebuffer: Use dma_buf from GEM object instance"

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This reverts commit cce16fcd74.

The dma_buf field in struct drm_gem_object is not stable over the
object instance's lifetime. The field becomes NULL when user space
releases the final GEM handle on the buffer object. This resulted
in a NULL-pointer deref.

Workarounds in commit 5307dce878 ("drm/gem: Acquire references on
GEM handles for framebuffers") and commit f6bfc9afc7 ("drm/framebuffer:
Acquire internal references on GEM handles") only solved the problem
partially. They especially don't work for buffer objects without a DRM
framebuffer associated.

Hence, this revert to going back to using .import_attach->dmabuf.

v3:
- cc stable

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Zack Rusin <zack.rusin@broadcom.com>
Cc: <stable@vger.kernel.org> # v6.15+
Link: https://lore.kernel.org/r/20250715155934.150656-6-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann
2025-07-15 17:58:15 +02:00
parent fb4ef4a52b
commit 2712ca878b
1 changed files with 6 additions and 2 deletions
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8
drivers/gpu/drm/drm_gem_framebuffer_helper.c
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@@ -419,6 +419,7 @@ EXPORT_SYMBOL(drm_gem_fb_vunmap);
static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_data_direction dir,
unsigned int num_planes)
{
struct dma_buf_attachment *import_attach;
struct drm_gem_object *obj;
int ret;
@@ -427,9 +428,10 @@ static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_dat
obj = drm_gem_fb_get_obj(fb, num_planes);
if (!obj)
continue;
import_attach = obj->import_attach;
if (!drm_gem_is_imported(obj))
continue;
ret = dma_buf_end_cpu_access(obj->dma_buf, dir);
ret = dma_buf_end_cpu_access(import_attach->dmabuf, dir);
if (ret)
drm_err(fb->dev, "dma_buf_end_cpu_access(%u, %d) failed: %d\n",
ret, num_planes, dir);
@@ -452,6 +454,7 @@ static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_dat
*/
int drm_gem_fb_begin_cpu_access(struct drm_framebuffer *fb, enum dma_data_direction dir)
{
struct dma_buf_attachment *import_attach;
struct drm_gem_object *obj;
unsigned int i;
int ret;
@@ -462,9 +465,10 @@ int drm_gem_fb_begin_cpu_access(struct drm_framebuffer *fb, enum dma_data_direct
ret = -EINVAL;
goto err___drm_gem_fb_end_cpu_access;
}
import_attach = obj->import_attach;
if (!drm_gem_is_imported(obj))
continue;
ret = dma_buf_begin_cpu_access(obj->dma_buf, dir);
ret = dma_buf_begin_cpu_access(import_attach->dmabuf, dir);
if (ret)
goto err___drm_gem_fb_end_cpu_access;
}