device_cgroup: fix unchecked cgroup parent usage
In 4cef7299b478687 ("device_cgroup: add proper checking when changing
default behavior") the cgroup parent usage is unchecked. root will not
have a parent and trying to use device.{allow,deny} will cause problems.
For some reason my stressing scripts didn't test the root directory so I
didn't catch it on my regular tests.
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: James Morris <jmorris@namei.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 842c254..96d87ea 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -352,6 +352,8 @@
*/
static inline int may_allow_all(struct dev_cgroup *parent)
{
+ if (!parent)
+ return 1;
return parent->behavior == DEVCG_DEFAULT_ALLOW;
}
@@ -376,11 +378,14 @@
int count, rc;
struct dev_exception_item ex;
struct cgroup *p = devcgroup->css.cgroup;
- struct dev_cgroup *parent = cgroup_to_devcgroup(p->parent);
+ struct dev_cgroup *parent = NULL;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ if (p->parent)
+ parent = cgroup_to_devcgroup(p->parent);
+
memset(&ex, 0, sizeof(ex));
b = buffer;
@@ -391,11 +396,14 @@
if (!may_allow_all(parent))
return -EPERM;
dev_exception_clean(devcgroup);
+ devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
+ if (!parent)
+ break;
+
rc = dev_exceptions_copy(&devcgroup->exceptions,
&parent->exceptions);
if (rc)
return rc;
- devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
break;
case DEVCG_DENY:
dev_exception_clean(devcgroup);