bpf: Fix wrong reg type conversion in release_reference()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix wrong reg type conversion in release_reference() Some helper functions will allocate memory. To avoid memory leaks, the verifier requires the eBPF program to release these memories by calling the corresponding helper functions. When a resource is released, all pointer registers corresponding to the resource should be invalidated. The verifier use release_references() to do this job, by apply __mark_reg_unknown() to each relevant register. It will give these registers the type of SCALAR_VALUE. A register that will contain a pointer value at runtime, but of type SCALAR_VALUE, which may allow the unprivileged user to get a kernel pointer by storing this register into a map. Using __mark_reg_not_init() while NOT allow_ptr_leaks can mitigate this problem.

References

• https://git.kernel.org/stable/c/cedd4f01f67be94735f15123158f485028571037
• https://git.kernel.org/stable/c/466ce46f251dfb259a8cbaa895ab9edd6fb56240
• https://git.kernel.org/stable/c/ae5ccad6c711db0f2ca1231be051935dd128b8f5
• https://git.kernel.org/stable/c/f1db20814af532f85e091231223e5e4818e8464b