[LTP] [PATCH v4 1/2] cgroup_core01.c: Set system default umaks to 0

[Wei Gao]

When system's default umask is 0077, this will trigger issues for LTP case.

cgroup_core01.c will report following error msg:
cgroup_core01.c:50: TBROK: openat(21</sys/fs/cgroup/memory/ltp/test-3519/child_b>, 'tasks', 2, 0): EACCES (13)

Detail reason:
Code:
cg_child_a = tst_cg_group_mk(tst_cg, "child_a");
cg_child_b = tst_cg_group_mk(tst_cg, "child_b");

Result:
wegao:/sys/fs/cgroup # ll ltp/test-25304/
drwx------ 2 root root 0 Feb 10 10:37 child_a   <<<<<< group and other has no any permission
drwx------ 2 root root 0 Feb 10 10:38 child_b

Code:
SAFE_CG_FCHOWN(cg_child_a, "cgroup.procs",  nobody_uid, -1);
SAFE_CG_FCHOWN(cg_child_b, "cgroup.procs",  nobody_uid, -1);

Result:
wegao:/sys/fs/cgroup # ll ltp/test-26388/child_a/
total 0
-rw-r--r-- 1 nobody root 0 Feb 10 10:44 cgroup.procs  <<<<<<

Code:
SAFE_SETEUID(nobody_uid); <<<< after switch to nobody then can not access child_{a,b} or any file
under child_{a,b}

Result:
nobody@wegao:/sys/fs/cgroup/ltp/test-26730> ll child_a/  <<< nobody has no permission on child_a
ls: cannot open directory 'child_a/': Permission denied

Code:
loops = SAFE_CG_OPEN(cg_child_b, "cgroup.procs", O_RDWR, fds);
Result:
cgroup_core01.c:76: TBROK: openat(9</sys/fs/cgroup/ltp/test-26388/child_b>, 'cgroup.procs', 2, 0): EACCES (13)

Signed-off-by: Wei Gao <wegao@suse.com>
---
 testcases/kernel/controllers/cgroup/cgroup_core01.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/testcases/kernel/controllers/cgroup/cgroup_core01.c b/testcases/kernel/controllers/cgroup/cgroup_core01.c
index 2e695deed..ad08c74a9 100644
--- a/testcases/kernel/controllers/cgroup/cgroup_core01.c
+++ b/testcases/kernel/controllers/cgroup/cgroup_core01.c
@@ -76,6 +76,8 @@ static void setup(void)
 {
 	struct passwd *pw;
 
+	umask(0);
+
 	pw = SAFE_GETPWNAM("nobody");
 	nobody_uid = pw->pw_uid;
 	save_uid = geteuid();
-- 
2.35.3