x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: x86/MCE/AMD: Fix memory leak when threshold_create_bank() fails In mce_threshold_create_device(), if threshold_create_bank() fails, the previously allocated threshold banks array @bp will be leaked because the call to mce_threshold_remove_device() will not free it. This happens because mce_threshold_remove_device() fetches the pointer through the threshold_banks per-CPU variable but bp is written there only after the bank creation is successful, and not before, when threshold_create_bank() fails. Add a helper which unwinds all the bank creation work previously done and pass into it the previously allocated threshold banks array for freeing. [ bp: Massage. ]

References

• https://git.kernel.org/stable/c/b4acb8e7f1594607bc9017ef0aacb40b24a003d6
• https://git.kernel.org/stable/c/cc0dd4456f9573bf8af9b4d8754433918e809e1e
• https://git.kernel.org/stable/c/9708f1956eeb70c86943e0bc62fa3b0101b59616
• https://git.kernel.org/stable/c/396b8e7ab2a99ddac57d3522b3da5e58cb608d37
• https://git.kernel.org/stable/c/e5f28623ceb103e13fc3d7bd45edf9818b227fd0