drm/panfrost: Fix GEM handle creation ref-counting

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/panfrost: Fix GEM handle creation ref-counting panfrost_gem_create_with_handle() previously returned a BO but with the only reference being from the handle, which user space could in theory guess and release, causing a use-after-free. Additionally if the call to panfrost_gem_mapping_get() in panfrost_ioctl_create_bo() failed then a(nother) reference on the BO was dropped. The _create_with_handle() is a problematic pattern, so ditch it and instead create the handle in panfrost_ioctl_create_bo(). If the call to panfrost_gem_mapping_get() fails then this means that user space has indeed gone behind our back and freed the handle. In which case just return an error code.

References

• https://git.kernel.org/stable/c/0b70f6ea4d4f2b4d4b291d86ab76b4d07394932c
• https://git.kernel.org/stable/c/4f1105ee72d8c7c35d90e3491b31b2d9d6b7e33a
• https://git.kernel.org/stable/c/3f9feffa8a5ab08b4e298a27b1aa7204a7d42ca2
• https://git.kernel.org/stable/c/ba3d2c2380e7129b525a787489c0b7e819a3b898
• https://git.kernel.org/stable/c/4217c6ac817451d5116687f3cc6286220dc43d49