Description: powerpc/perf: Fix crash in perf_instruction_pointer() when ppmu is not set
References:
Notes:
 carnil> Commit fixes 2ca13a4cc56c ("powerpc/perf: Use regs->nip when
 carnil> SIAR is zero") so might not affect earlier versions.
Bugs:
upstream: released (5.13-rc7) [60b7ed54a41b550d50caf7f2418db4a7e75b5bdc]
5.10-upstream-stable: N/A "vulnerable code introduced later"
4.19-upstream-stable: N/A "vulnerable code introduced later"
4.9-upstream-stable: N/A "vulnerable code introduced later"
sid: N/A "vulnerable code introduced later"
5.10-bullseye-security: N/A "vulnerable code introduced later"
4.19-buster-security: N/A "vulnerable code introduced later"
4.9-stretch-security: N/A "vulnerable code introduced later"