drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a dma_fence obj

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/amd/amdgpu/amdgpu_cs: fix refcount leak of a dma_fence obj This issue takes place in an error path in amdgpu_cs_fence_to_handle_ioctl(). When `info->in.what` falls into default case, the function simply returns -EINVAL, forgetting to decrement the reference count of a dma_fence obj, which is bumped earlier by amdgpu_cs_get_fence(). This may result in reference count leaks. Fix it by decreasing the refcount of specific object before returning the error code.

References

• https://git.kernel.org/stable/c/72d77ddb2224ebc00648f4f78f8a9a259dccbdf7
• https://git.kernel.org/stable/c/4009f104b02b223d1a11d74b36b1cc083bc37028
• https://git.kernel.org/stable/c/927beb05aaa429c883cc0ec6adc48964b187e291
• https://git.kernel.org/stable/c/3edd8646cb7c11b57c90e026bda6f21076223f5b
• https://git.kernel.org/stable/c/b6d1f7d97c81ebaf2cda9c4c943ee2e484fffdcf
• https://git.kernel.org/stable/c/bc2d5c0775c839e2b072884f4ee6a93ba410f107
• https://git.kernel.org/stable/c/dfced44f122c500004a48ecc8db516bb6a295a1b