perf jevents: Fix suspicious code in fixregex()

The new string should have enough space for the original string and the
back slashes IMHO.

Fixes: fbc2844e ("perf vendor events: Use more flexible pattern matching for CPU identification for mapfile.csv")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: William Cohen <wcohen@redhat.com>
Link: http://lore.kernel.org/lkml/20200903152510.489233-1-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/pmu-events/jevents.c

@@ -137,7 +137,7 @@ static char *fixregex(char *s)
 		return s;
 
 	/* allocate space for a new string */
-	fixed = (char *) malloc(len + 1);
+	fixed = (char *) malloc(len + esc_count + 1);
 	if (!fixed)
 		return NULL;