On 5/27/22 01:50, Dmitry Osipenko wrote:
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. For example, 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.
To fix this bug, move mapping of imported dma-bufs to drm_gem_mmap_obj(). Now mmaping of imported dma-bufs works properly for all DRM drivers.
Same comment about Fixes: as in patch 1,
Cc: stable@vger.kernel.org Signed-off-by: Dmitry Osipenko dmitry.osipenko@collabora.com
drivers/gpu/drm/drm_gem.c | 3 +++ drivers/gpu/drm/drm_gem_shmem_helper.c | 9 --------- drivers/gpu/drm/tegra/gem.c | 4 ++++ 3 files changed, 7 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index 86d670c71286..7c0b025508e4 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1038,6 +1038,9 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size, if (obj_size < vma->vm_end - vma->vm_start) return -EINVAL;
- if (obj->import_attach)
return dma_buf_mmap(obj->dma_buf, vma, 0);
If we start enabling mmaping of imported dma-bufs on a majority of drivers in this way, how do we ensure that user-space is not blindly using the object mmap without calling the needed DMA_BUF_IOCTL_SYNC which is needed before and after cpu access of mmap'ed dma-bufs?
I was under the impression (admittedly without looking) that the few drivers that actually called into dma_buf_mmap() had some private user-mode driver code in place that ensured this happened.
/Thomas
- /* Take a ref for this mapping of the object, so that the fault
- handler can dereference the mmap offset's pointer to the object.
- This reference is cleaned up by the corresponding vm_close
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);
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c index 7c7dd84e6db8..f92aa20d63bb 100644 --- a/drivers/gpu/drm/tegra/gem.c +++ b/drivers/gpu/drm/tegra/gem.c @@ -564,6 +564,10 @@ int __tegra_gem_mmap(struct drm_gem_object *gem, struct vm_area_struct *vma) { struct tegra_bo *bo = to_tegra_bo(gem);
- /* imported dmu-buf is mapped by drm_gem_mmap_obj() */
- if (gem->import_attach)
return 0;- if (!bo->pages) { unsigned long vm_pgoff = vma->vm_pgoff; int err;