perf tools: Check $HOME/.perfconfig ownership

Just like we do already for perf.data files.
Requested-by: Ingo Molnar <mingo@elte.hu>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Christian Ohm <chr.ohm@gmx.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jonathan Nieder <jrnieder@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-qgokmxsmvppwpc5404qhyk7e@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/config.c

@@ -413,13 +413,32 @@ int perf_config(config_fn_t fn, void *data)
 	home = getenv("HOME");
 	if (perf_config_global() && home) {
 		char *user_config = strdup(mkpath("%s/.perfconfig", home));
-		if (!access(user_config, R_OK)) {
-			ret += perf_config_from_file(fn, user_config, data);
-			found += 1;
+		struct stat st;
+
+		if (user_config == NULL) {
+			warning("Not enough memory to process %s/.perfconfig, "
+				"ignoring it.", home);
+			goto out;
+		}
+
+		if (stat(user_config, &st) < 0)
+			goto out_free;
+
+		if (st.st_uid && (st.st_uid != geteuid())) {
+			warning("File %s not owned by current user or root, "
+				"ignoring it.", user_config);
+			goto out_free;
 		}
+
+		if (!st.st_size)
+			goto out_free;
+
+		ret += perf_config_from_file(fn, user_config, data);
+		found += 1;
+out_free:
 		free(user_config);
 	}
-
+out:
 	if (found == 0)
 		return -1;
 	return ret;