In the Linux kernel, the following vulnerability has been resolved: drm/prime: Fix use after free in mmap with drmgemttmmmap drmgemttmmmap() drops a reference to the gem object on success. If the gem object's refcount == 1 on entry to drmgemprimemmap(), that drop will free the gem object, and the subsequent drmgemobjectget() will be a UAF. Fix by grabbing a reference before calling the mmap helper. This issue was forseen when the reference dropping was adding in commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"): "For that to work properly the drmgemobjectget() call in drmgemttmmmap() must be moved so it happens before calling obj->funcs->mmap(), otherwise the gem refcount would go down to zero."