Quoting a...@redhat.com (a...@redhat.com):
> In preparation for better hierarchy support, it's needed to retain the local
> settings in order to try to reapply them after a propagated change if they're
> still valid.
>
> v2: split this patch in two, one to just move dev_exception_rm() before
> dev_exception_add() while keeping functional changes in this patch as
> requested by Tejun.
>
> Acked-by: Tejun Heo <t...@kernel.org>
> Cc: Tejun Heo <t...@kernel.org>
> Cc: Serge Hallyn <serge.hal...@canonical.com>
Acked-by: Serge Hallyn <serge.hal...@canonical.com>
> Signed-off-by: Aristeu Rozanski <a...@redhat.com>
>
> ---
> security/device_cgroup.c | 83
> +++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 67 insertions(+), 16 deletions(-)
>
> --- github.orig/security/device_cgroup.c 2013-01-29 11:49:14.987661210
> -0500
> +++ github/security/device_cgroup.c 2013-01-29 11:49:15.244665037 -0500
> @@ -39,13 +39,27 @@ struct dev_exception_item {
> struct rcu_head rcu;
> };
>
> +enum devcg_behavior {
> + DEVCG_DEFAULT_NONE,
> + DEVCG_DEFAULT_ALLOW,
> + DEVCG_DEFAULT_DENY,
> +};
> +
> struct dev_cgroup {
> struct cgroup_subsys_state css;
> +
> + /* result of merging the parent's rules with local ones */
> struct list_head exceptions;
> - enum {
> - DEVCG_DEFAULT_ALLOW,
> - DEVCG_DEFAULT_DENY,
> - } behavior;
> + enum devcg_behavior behavior;
> +
> + /*
> + * local set rules, saved so when a parent propagates new rules, the
> + * local preferences can be preserved
> + */
> + struct {
> + struct list_head exceptions;
> + enum devcg_behavior behavior;
> + } local;
> };
>
> static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state
> *s)
> @@ -104,8 +118,8 @@ free_and_exit:
> /*
> * called under devcgroup_mutex
> */
> -static void dev_exception_rm(struct list_head *exceptions,
> - struct dev_exception_item *ex)
> +static void __dev_exception_rm(struct list_head *exceptions,
> + struct dev_exception_item *ex)
> {
> struct dev_exception_item *walk, *tmp;
>
> @@ -127,11 +141,18 @@ static void dev_exception_rm(struct list
> }
> }
>
> +static void dev_exception_rm(struct dev_cgroup *devcgroup,
> + struct dev_exception_item *ex)
> +{
> + __dev_exception_rm(&devcgroup->local.exceptions, ex);
> + __dev_exception_rm(&devcgroup->exceptions, ex);
> +}
> +
> /*
> * called under devcgroup_mutex
> */
> -static int dev_exception_add(struct list_head *exceptions,
> - struct dev_exception_item *ex)
> +static int __dev_exception_add(struct list_head *exceptions,
> + struct dev_exception_item *ex)
> {
> struct dev_exception_item *excopy, *walk;
>
> @@ -159,6 +180,28 @@ static int dev_exception_add(struct list
> return 0;
> }
>
> +static int dev_exception_add(struct dev_cgroup *devcgroup,
> + struct dev_exception_item *ex)
> +{
> + int rc;
> +
> + lockdep_assert_held(&devcgroup_mutex);
> +
> + /*
> + * we add to the local list so we can preserve local preferences if
> + * the parent propagates down new rules
> + */
> + rc = __dev_exception_add(&devcgroup->local.exceptions, ex);
> + if (rc)
> + return rc;
> +
> + rc = __dev_exception_add(&devcgroup->exceptions, ex);
> + if (rc)
> + __dev_exception_rm(&devcgroup->local.exceptions, ex);
> +
> + return rc;
> +}
> +
> static void __dev_exception_clean(struct dev_cgroup *dev_cgroup)
> {
> struct dev_exception_item *ex, *tmp;
> @@ -167,6 +210,11 @@ static void __dev_exception_clean(struct
> list_del_rcu(&ex->list);
> kfree_rcu(ex, rcu);
> }
> + list_for_each_entry_safe(ex, tmp, &dev_cgroup->local.exceptions,
> + list) {
> + list_del_rcu(&ex->list);
> + kfree_rcu(ex, rcu);
> + }
> }
>
> /**
> @@ -195,6 +243,8 @@ static struct cgroup_subsys_state *devcg
> if (!dev_cgroup)
> return ERR_PTR(-ENOMEM);
> INIT_LIST_HEAD(&dev_cgroup->exceptions);
> + INIT_LIST_HEAD(&dev_cgroup->local.exceptions);
> + dev_cgroup->local.behavior = DEVCG_DEFAULT_NONE;
> parent_cgroup = cgroup->parent;
>
> if (parent_cgroup == NULL)
> @@ -413,18 +463,19 @@ memset(&ex, 0, sizeof(ex));
> if (!may_allow_all(parent))
> return -EPERM;
> dev_exception_clean(devcgroup);
> + if (parent)
> + rc = dev_exceptions_copy(&devcgroup->exceptions,
> + &parent->exceptions);
> devcgroup->behavior = DEVCG_DEFAULT_ALLOW;
> - if (!parent)
> - break;
> + devcgroup->local.behavior = DEVCG_DEFAULT_ALLOW;
>
> - rc = dev_exceptions_copy(&devcgroup->exceptions,
> - &parent->exceptions);
> if (rc)
> return rc;
> break;
> case DEVCG_DENY:
> dev_exception_clean(devcgroup);
> devcgroup->behavior = DEVCG_DEFAULT_DENY;
> + devcgroup->local.behavior = DEVCG_DEFAULT_DENY;
> break;
> default:
> return -EINVAL;
> @@ -514,10 +565,10 @@ case '\0':
> * don't want to break compatibility
> */
> if (devcgroup->behavior == DEVCG_DEFAULT_ALLOW) {
> - dev_exception_rm(&devcgroup->exceptions, &ex);
> + dev_exception_rm(devcgroup, &ex);
> return 0;
> }
> - return dev_exception_add(&devcgroup->exceptions, &ex);
> + return dev_exception_add(devcgroup, &ex);
> case DEVCG_DENY:
> /*
> * If the default policy is to deny by default, try to remove
> @@ -525,10 +576,10 @@ return 0;
> * don't want to break compatibility
> */
> if (devcgroup->behavior == DEVCG_DEFAULT_DENY) {
> - dev_exception_rm(&devcgroup->exceptions, &ex);
> + dev_exception_rm(devcgroup, &ex);
> return 0;
> }
> - return dev_exception_add(&devcgroup->exceptions, &ex);
> + return dev_exception_add(devcgroup, &ex);
> default:
> return -EINVAL;
> }
>
> --
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