Commit 65ad8e0a authored by Ondrej Mosnáček's avatar Ondrej Mosnáček Committed by Greg Kroah-Hartman

cgroup: fix parsing empty mount option string

[ Upstream commit e250d91d ]

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: 67e9c74b ("cgroup: replace __DEVEL__sane_behavior with cgroup2 fs type")
[NOTE: should apply on top of commit 5136f636 ("cgroup: implement "nsdelegate" mount option"), older versions need manual rebase]
Suggested-by: Stephen Smalley's avatarStephen Smalley <>
Signed-off-by: Ondrej Mosnáček's avatarOndrej Mosnacek <>
Signed-off-by: 's avatarTejun Heo <>
Signed-off-by: 's avatarSasha Levin <>
parent 478fec4a
......@@ -1744,7 +1744,7 @@ 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) {
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