On Tue, Jul 15, 2025 at 10:26:22AM +0200, Thomas Zimmermann wrote: > This reverts commit 515986100d176663d0a03219a3056e4252f729e6. > > 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 5307dce878d4 ("drm/gem: Acquire references on > GEM handles for framebuffers") and commit f6bfc9afc751 ("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. > > Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
Reviewed-by: Simona Vetter <simona.vet...@ffwll.ch> > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 2 +- > drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 3 ++- > drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +- > 3 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > index ff98c87b2e0b..5743ebb2f1b7 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > @@ -514,7 +514,7 @@ bool amdgpu_dmabuf_is_xgmi_accessible(struct > amdgpu_device *adev, > return false; > > if (drm_gem_is_imported(obj)) { > - struct dma_buf *dma_buf = obj->dma_buf; > + struct dma_buf *dma_buf = obj->import_attach->dmabuf; > > if (dma_buf->ops != &amdgpu_dmabuf_ops) > /* No XGMI with non AMD GPUs */ > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c > index 6626a6e64ff5..d1ccbfcf21fa 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c > @@ -317,7 +317,8 @@ static int amdgpu_gem_object_open(struct drm_gem_object > *obj, > */ > if (!vm->is_compute_context || !vm->process_info) > return 0; > - if (!drm_gem_is_imported(obj) || !dma_buf_is_dynamic(obj->dma_buf)) > + if (!drm_gem_is_imported(obj) || > + !dma_buf_is_dynamic(obj->import_attach->dmabuf)) > return 0; > mutex_lock_nested(&vm->process_info->lock, 1); > if (!WARN_ON(!vm->process_info->eviction_fence)) { > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c > index af0f655dfd5b..b9b4f7d9186e 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c > @@ -1272,7 +1272,7 @@ int amdgpu_vm_bo_update(struct amdgpu_device *adev, > struct amdgpu_bo_va *bo_va, > struct drm_gem_object *obj = &bo->tbo.base; > > if (drm_gem_is_imported(obj) && bo_va->is_xgmi) { > - struct dma_buf *dma_buf = obj->dma_buf; > + struct dma_buf *dma_buf = obj->import_attach->dmabuf; > struct drm_gem_object *gobj = dma_buf->priv; > struct amdgpu_bo *abo = gem_to_amdgpu_bo(gobj); > > -- > 2.50.0 > -- Simona Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch