device_cgroup: fix unchecked cgroup parent usage (64e10477) · Commits · 戴 / test

In ("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>

security/device_cgroup.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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);

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