Quoting a...@redhat.com (a...@redhat.com):
> Currently may_access() is only able to verify if an exception is valid for the
> current cgroup, which has the same behavior. With hierarchy, it'll be also
> used
> to verify if a cgroup local exception is valid towards its cgroup parent,
> which
> might have different behavior.
>
> v2:
> - updated patch description
> - rebased on top of a new patch to expand the may_access() logic to make it
> more clear
> - fixed argument description order in may_access()
>
> 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 | 38 ++++++++++++++++++++++++--------------
> 1 file changed, 24 insertions(+), 14 deletions(-)
>
> --- github.orig/security/device_cgroup.c 2013-01-30 08:58:02.000000000
> -0500
> +++ github/security/device_cgroup.c 2013-01-30 09:00:09.435351867 -0500
> @@ -354,9 +354,11 @@ return 0;
> * verify if a certain access is allowed.
> * @dev_cgroup: dev cgroup to be tested against
> * @refex: new exception
> + * @behavior: behavior of the exception
> */
> static bool may_access(struct dev_cgroup *dev_cgroup,
> - struct dev_exception_item *refex)
> + struct dev_exception_item *refex,
> + enum devcg_behavior behavior)
> {
> struct dev_exception_item *ex;
> bool match = false;
> @@ -380,19 +382,27 @@ if (ex->minor != ~0 && ex->minor != re
> break;
> }
>
> - /*
> - * In two cases we'll consider this new exception valid:
> - * - the dev cgroup has its default policy to deny + exception list:
> - * the new exception *should* match the exceptions
> - * - the dev cgroup has its default policy to allow + exception list:
> - * the new exception should *not* match any of the exceptions
> - */
> - if (dev_cgroup->behavior == DEVCG_DEFAULT_DENY) {
> - if (match)
> + if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
> + if (behavior == DEVCG_DEFAULT_ALLOW) {
> + /* the exception will deny access to certain devices */
> return true;
> + } else {
> + /* the exception will allow access to certain devices */
> + if (match)
> + /*
> + * a new exception allowing access shouldn't
> + * match an parent's exception
> + */
> + return false;
> + return true;
> + }
> } else {
> - if (!match)
> + /* only behavior == DEVCG_DEFAULT_DENY allowed here */
> + if (match)
> + /* parent has an exception that matches the proposed */
> return true;
> + else
> + return false;
> }
> return false;
> }
> @@ -411,7 +421,7 @@ static int parent_has_perm(struct dev_cg
> if (!pcg)
> return 1;
> parent = cgroup_to_devcgroup(pcg);
> - return may_access(parent, ex);
> + return may_access(parent, ex, childcg->behavior);
> }
>
> /**
> @@ -445,7 +455,7 @@ static int devcgroup_update_access(struc
> {
> const char *b;
> char temp[12]; /* 11 + 1 characters needed for a u32 */
> - int count, rc;
> + int count, rc = 0;
This here points out that (unrelated to yor set) devcgroup_update_access()
really needs a cleanup.
> struct dev_exception_item ex;
> struct cgroup *p = devcgroup->css.cgroup;
> struct dev_cgroup *parent = NULL;
> @@ -663,7 +673,7 @@ memset(&ex, 0, sizeof(ex));
>
> rcu_read_lock();
> dev_cgroup = task_devcgroup(current);
> - rc = may_access(dev_cgroup, &ex);
> + rc = may_access(dev_cgroup, &ex, dev_cgroup->behavior);
> rcu_read_unlock();
>
> if (!rc)
>
> --
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