cgroup: fix parsing empty mount option string

This fixes the case where all mount options specified are consumed by an
LSM and all that's left is an empty string. In this case cgroupfs should
accept the string and not fail.

How to reproduce (with SELinux enabled):

    # umount /sys/fs/cgroup/unified
    # mount -o context=system_u:object_r:cgroup_t:s0 -t cgroup2 cgroup2 /sys/fs/cgroup/unified
    mount: /sys/fs/cgroup/unified: wrong fs type, bad option, bad superblock on cgroup2, missing codepage or helper program, or other error.
    # dmesg | tail -n 1
    [   31.575952] cgroup: cgroup2: unknown option ""

Fixes: 67e9c74b8a ("cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type")
[NOTE: should apply on top of commit 5136f6365c ("cgroup: implement "nsdelegate" mount option"), older versions need manual rebase]
Suggested-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Ondrej Mosnacek 2018-12-13 15:17:37 +01:00 committed by Tejun Heo
parent 4d71c6f877
commit e250d91d65

View File

@ -1748,7 +1748,7 @@ static int parse_cgroup_root_flags(char *data, unsigned int *root_flags)
*root_flags = 0;
if (!data)
if (!data || *data == '\0')
return 0;
while ((token = strsep(&data, ",")) != NULL) {