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device_cgroup: fix unchecked cgroup parent usage 

In 4cef7299b4 ("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>
This commit is contained in:
Aristeu Rozanski 2012-11-06 07:25:04 -08:00 committed by Tejun Heo
parent 3d70f8c617
commit 64e1047713
1 changed files with 10 additions and 2 deletions
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12
security/device_cgroup.c
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@ -352,6 +352,8 @@ static int parent_has_perm(struct dev_cgroup *childcg,
*/
static inline int may_allow_all(struct dev_cgroup *parent)
{
if (!parent)
return 1;
return parent->behavior == DEVCG_DEFAULT_ALLOW;
}
@ -376,11 +378,14 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
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);