perf MachineResolve OOB

Vulnerability analysis

When the perf tool resolves samples from a perf.data file, it reads CPU topology information using a CPU index taken directly from the file without checking it against the number of CPUs actually recorded. A crafted file with an out-of-range CPU index causes the tool to read past the end of the topology array on the heap, leaking memory. Additionally, large values could silently truncate when cast to a narrower integer type, causing incorrect topology lookups. The fix validates the CPU index against the available count before any access and uses a bounds-checking accessor, preventing both the over-read and the truncation bypass. The vulnerable path is reached whenever the perf tool processes a perf.data file, so an attacker who can supply or trick a user into analyzing such a file can trigger the read.