Messages in this thread Patch in this message | | | Date | Tue, 5 Jul 2022 13:39:20 +0200 | Subject | Re: [PATCH v8 2/2] drm/gem: Don't map imported GEMs | From | Christian König <> |
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Am 01.07.22 um 11:02 schrieb Dmitry Osipenko: > Drivers that use drm_gem_mmap() and drm_gem_mmap_obj() helpers don't > handle imported dma-bufs properly, which results in mapping of something > else than the imported dma-buf. On NVIDIA Tegra we get a hard lockup when > userspace writes to the memory mapping of a dma-buf that was imported into > Tegra's DRM GEM. > > Majority of DRM drivers prohibit mapping of the imported GEM objects. > Mapping of imported GEMs require special care from userspace since it > should sync dma-buf because mapping coherency of the exporter device may > not match the DRM device. Let's prohibit the mapping for all DRM drivers > for consistency. > > Suggested-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
I'm pretty sure that this is the right approach, but it's certainly more than possible that somebody abused this already.
Anyway patch is Reviewed-by: Christian König <christian.koenig@amd.com> since you are really fixing a major stability problem here.
Regards, Christian.
> --- > drivers/gpu/drm/drm_gem.c | 4 ++++ > drivers/gpu/drm/drm_gem_shmem_helper.c | 9 --------- > 2 files changed, 4 insertions(+), 9 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index 86d670c71286..fc9ec42fa0ab 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -1034,6 +1034,10 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size, > { > int ret; > > + /* Don't allow imported objects to be mapped */ > + if (obj->import_attach) > + return -EINVAL; > + > /* Check for valid size. */ > if (obj_size < vma->vm_end - vma->vm_start) > return -EINVAL; > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 8ad0e02991ca..6190f5018986 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -609,17 +609,8 @@ EXPORT_SYMBOL_GPL(drm_gem_shmem_vm_ops); > */ > int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct *vma) > { > - struct drm_gem_object *obj = &shmem->base; > int ret; > > - if (obj->import_attach) { > - /* Drop the reference drm_gem_mmap_obj() acquired.*/ > - drm_gem_object_put(obj); > - vma->vm_private_data = NULL; > - > - return dma_buf_mmap(obj->dma_buf, vma, 0); > - } > - > ret = drm_gem_shmem_get_pages(shmem); > if (ret) { > drm_gem_vm_close(vma);
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