KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: KVM: s390/diag: fix racy access of physical cpu number in diag 9c handler We do check for target CPU == -1, but this might change at the time we are going to use it. Hold the physical target CPU in a local variable to avoid out-of-bound accesses to the cpu arrays.

References

• https://git.kernel.org/stable/c/a9ccf140a2a03a0ae82be4bdfbdd17bdaea72ff5
• https://git.kernel.org/stable/c/86bfb18bad60fc468e5f112cbbd918462a8dd435
• https://git.kernel.org/stable/c/dc7e0192c470a53d847c79a2796f9ac429477a26
• https://git.kernel.org/stable/c/0bc380beb78aa352eadbc21d934dd9606fcee808