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No it can't, IIRC sync files are only supposed to contain raw fences or dma_fence_array containers. I think we never documented that and that's why this issue here leaked in. I'm not sure if that doesn't break anywhere else as well, so I think we should fix the exporting side instead. Alternatively we need to audit everywhere where fences from syncfiles can be imported somewhere else. Regards, Christian. > Importing such a sync_file into a timeline point with > DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_IMPORT_SYNC_FILE | > DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_TIMELINE passes the chain directly to > dma_fence_chain_init() and triggers > > WARNING: drivers/dma-buf/dma-fence-chain.c:286 at dma_fence_chain_init > > because chain fences must not be wrapped in other chain fences. > > Flatten the fence with dma_fence_unwrap_merge() before adding it to the > timeline, as drm_syncobj_transfer_to_timeline() already does. > > Reproducer: > > 1. Export a sync_file from a point > 0 of a timeline syncobj with > DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD. > 2. Import it into a point > 0 of another timeline syncobj with > DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE. > > Fixes: c2d3a7300695 ("drm/syncobj: Extend EXPORT_SYNC_FILE for timeline syncobjs") > Assisted-by: Claude:claude-opus-5-5 > Signed-off-by: Julian Orth > --- > drivers/gpu/drm/drm_syncobj.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c > index 5ca5163d0..c545af77e 100644 > --- a/drivers/gpu/drm/drm_syncobj.c > +++ b/drivers/gpu/drm/drm_syncobj.c > @@ -742,8 +742,18 @@ static int drm_syncobj_import_sync_file_fence(struct drm_file *file_private, > } > > if (point) { > - struct dma_fence_chain *chain = dma_fence_chain_alloc(); > + struct dma_fence_chain *chain; > + struct dma_fence *tmp; > + > + tmp = dma_fence_unwrap_merge(fence); > + dma_fence_put(fence); > + fence = tmp; > + if (!fence) { > + drm_syncobj_put(syncobj); > + return -ENOMEM; > + } > > + chain = dma_fence_chain_alloc(); > if (!chain) { > ret = -ENOMEM; > goto out;