On Mon, May 30, 2022 at 12:26 AM Thomas Zimmermann tzimmermann@suse.de wrote:
Hi
Am 29.05.22 um 18:29 schrieb Rob Clark:
From: Rob Clark robdclark@chromium.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().
Which drivers are affected by this problem?
I checked several drivers and most appear to be initializing the offset during object construction, such as GEM SHMEM. [1] TTM-based drivers also seem unaffected. [2]
From a quick grep, only etnaviv, msm and omapdrm appear to be affected? They only seem to run drm_gem_create_mmap_offset() from their ioctl-handling code.
If so, I'd say it's preferable to fix these drivers and put a drm_WARN_ONCE() into drm_gem_prime_mmap().
That is good if fewer drivers are affected, however I disagree with your proposal. At least for freedreno userspace, a lot of bo's never get mmap'd (either directly of via dmabuf), so we should not be allocating a mmap offset unnecessarily.
BR, -R
Best regards Thomas
[1] https://elixir.bootlin.com/linux/v5.18/source/drivers/gpu/drm/drm_gem_shmem_... [2] https://elixir.bootlin.com/linux/v5.18/source/drivers/gpu/drm/ttm/ttm_bo.c#L...
Fixes: e5516553999f ("drm: call drm_gem_object_funcs.mmap with fake offset") Signed-off-by: Rob Clark robdclark@chromium.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);-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev