[PATCH 4/4] device_cgroup: add proper checking when changing default behavior
From: Aristeu Rozanski <hidden>
Date: 2012-10-22 13:45:57
Also in:
lkml
Before changing a group's default behavior to ALLOW, we must check if its parent's behavior is also ALLOW. Cc: Tejun Heo <tj@kernel.org> Cc: Li Zefan <redacted> Cc: James Morris <jmorris@namei.org> Cc: Pavel Emelyanov <redacted> Cc: Serge Hallyn <redacted> Cc: Jiri Slaby <redacted> Signed-off-by: Aristeu Rozanski <redacted> --- security/device_cgroup.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
--- github.orig/security/device_cgroup.c 2012-10-19 16:36:50.135790476 -0400
+++ github/security/device_cgroup.c 2012-10-19 16:48:50.710978125 -0400@@ -344,6 +344,17 @@ static int parent_has_perm(struct dev_cg return may_access(parent, ex); } +/** + * may_allow_all - checks if it's possible to change the behavior to + * allow based on parent's rules. + * @parent: device cgroup's parent + * returns: != 0 in case it's allowed, 0 otherwise + */ +static inline int may_allow_all(struct dev_cgroup *parent) +{ + return parent->behavior == DEVCG_DEFAULT_ALLOW; +} + /* * Modify the exception list using allow/deny rules. * CAP_SYS_ADMIN is needed for this. It's at least separate from CAP_MKNOD
@@ -364,6 +375,8 @@ static int devcgroup_update_access(struc char temp[12]; /* 11 + 1 characters needed for a u32 */ int count, rc; struct dev_exception_item ex; + struct cgroup *p = devcgroup->css.cgroup; + struct dev_cgroup *parent = cgroup_to_devcgroup(p->parent); if (!capable(CAP_SYS_ADMIN)) return -EPERM;
@@ -375,9 +388,13 @@ memset(&ex, 0, sizeof(ex)); case 'a': switch (filetype) { case DEVCG_ALLOW: - if (!parent_has_perm(devcgroup, &ex)) + if (!may_allow_all(parent)) return -EPERM; dev_exception_clean(devcgroup); + rc = dev_exceptions_copy(&devcgroup->exceptions, + &parent->exceptions); + if (rc) + return rc; devcgroup->behavior = DEVCG_DEFAULT_ALLOW; break; case DEVCG_DENY: