UBUNTU: SAUCE: AppArmor: Fix oops there is no tracer and doing unsafe transition.
SRU Justification: This bug can cause confined process to oops at address 0.
This can occur when executing a process if the LSM_UNSAFE_PTRACE |
LSM_UNSAFE_PTRACE_CAP flags are set. The likely hood of if/how often this
will occur depends on if ptrace is being used.
As reported by Tetsuo Handa on kernel-team mailing list:
In aa_may_change_ptraced_domain, if (!tracer) cred == NULL, and
put_cred(cred) will oops. This will only happen on exec if the task
is marked as LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP, so should
only happen to ptraced tasks that are confined.
Fix this by returning directly from aa_may_change_ptrace_domain if
there is now tracer.