Before changing a group's default behavior to ALLOW, we must check if its
parent's behavior is also ALLOW.
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Aristeu Rozanski <aris@xxxxxxxxxx>
---
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:
--
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