This is a note to let you know that I've just added the patch titled

drm/shme-helpers: Fix dma_buf_mmap forwarding bug

to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: drm-shme-helpers-fix-dma_buf_mmap-forwarding-bug.patch and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From f49a51bfdc8ea717c97ccd4cc98b7e6daaa5553a Mon Sep 17 00:00:00 2001

From: Daniel Vetter daniel.vetter@ffwll.ch Date: Tue, 27 Oct 2020 22:49:22 +0100 Subject: drm/shme-helpers: Fix dma_buf_mmap forwarding bug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Daniel Vetter daniel.vetter@ffwll.ch

commit f49a51bfdc8ea717c97ccd4cc98b7e6daaa5553a upstream.

When we forward an mmap to the dma_buf exporter, they get to own everything. Unfortunately drm_gem_mmap_obj() overwrote vma->vm_private_data after the driver callback, wreaking the exporter complete. This was noticed because vb2_common_vm_close blew up on mali gpu with panfrost after commit 26d3ac3cb04d ("drm/shmem-helpers: Redirect mmap for imported dma-buf").

Unfortunately drm_gem_mmap_obj also acquires a surplus reference that we need to drop in shmem helpers, which is a bit of a mislayer situation. Maybe the entire dma_buf_mmap forwarding should be pulled into core gem code.

Note that the only two other drivers which forward mmap in their own code (etnaviv and exynos) get this somewhat right by overwriting the gem mmap code. But they seem to still have the leak. This might be a good excuse to move these drivers over to shmem helpers completely.

Reviewed-by: Boris Brezillon boris.brezillon@collabora.com Acked-by: Christian König christian.koenig@amd.com Cc: Christian König christian.koenig@amd.com Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Lucas Stach l.stach@pengutronix.de Cc: Russell King linux+etnaviv@armlinux.org.uk Cc: Christian Gmeiner christian.gmeiner@gmail.com Cc: Inki Dae inki.dae@samsung.com Cc: Joonyoung Shim jy0922.shim@samsung.com Cc: Seung-Woo Kim sw0312.kim@samsung.com Cc: Kyungmin Park kyungmin.park@samsung.com Fixes: 26d3ac3cb04d ("drm/shmem-helpers: Redirect mmap for imported dma-buf") Cc: Boris Brezillon boris.brezillon@collabora.com Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Gerd Hoffmann kraxel@redhat.com Cc: Rob Herring robh@kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Cc: stable@vger.kernel.org # v5.9+ Reported-and-tested-by: piotr.oniszczuk@gmail.com Cc: piotr.oniszczuk@gmail.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20201027214922.3566743-1-danie... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- drivers/gpu/drm/drm_gem.c | 4 ++-- drivers/gpu/drm/drm_gem_shmem_helper.c | 7 ++++++- 2 files changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1085,6 +1085,8 @@ int drm_gem_mmap_obj(struct drm_gem_obje */ drm_gem_object_get(obj);

+ vma->vm_private_data = obj; + if (obj->funcs && obj->funcs->mmap) { ret = obj->funcs->mmap(obj, vma); if (ret) { @@ -1107,8 +1109,6 @@ int drm_gem_mmap_obj(struct drm_gem_obje vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); }

- vma->vm_private_data = obj; - return 0; } EXPORT_SYMBOL(drm_gem_mmap_obj); --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -594,8 +594,13 @@ int drm_gem_shmem_mmap(struct drm_gem_ob /* Remove the fake offset */ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);

- if (obj->import_attach) + 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); + }

shmem = to_drm_gem_shmem_obj(obj);

Patches currently in stable-queue which might be from daniel.vetter@ffwll.ch are

queue-5.9/drm-ast-separate-drm-driver-from-pci-code.patch queue-5.9/drm-shme-helpers-fix-dma_buf_mmap-forwarding-bug.patch