perf symbols: Check kptr_restrict for root

If kptr_restrict is set to 2, even root is not allowed to see pointers.
This patch checks kptr_restrict even if euid == 0. For root, report
error if kptr_restrict is 2.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464081688-167940-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 20f9cb3..54c4ff2 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1933,17 +1933,17 @@ int setup_intlist(struct intlist **list, const char *list_str,
 static bool symbol__read_kptr_restrict(void)
 {
        bool value = false;
+       FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
 
-       if (geteuid() != 0) {
-               FILE *fp = fopen("/proc/sys/kernel/kptr_restrict", "r");
-               if (fp != NULL) {
-                       char line[8];
+       if (fp != NULL) {
+               char line[8];
 
-                       if (fgets(line, sizeof(line), fp) != NULL)
-                               value = atoi(line) != 0;
+               if (fgets(line, sizeof(line), fp) != NULL)
+                       value = (geteuid() != 0) ?
+                                       (atoi(line) != 0) :
+                                       (atoi(line) == 2);
 
-                       fclose(fp);
-               }
+               fclose(fp);
        }
 
        return value;