Andy Lutomirski pointed out that the current behavior of allowing the
owner of a user namespace to have all caps when that owner is not in a
parent user namespace is wrong.
This is a bug introduced by the kuid conversion which made it possible
for the owner of a user namespace to live in a child user namespace. I
goofed and totally missed this implication.
Serge and can you please take a look and see if my corrected cap_capable
reads correctly to you.
Andy or anyone else that wants to give me a second eyeball and double
check me on this I would appreciate it.
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
diff --git a/security/commoncap.c b/security/commoncap.c
index 6dbae46..4639f44 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -70,37 +70,44 @@ int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
*
* NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
* and has_capability() functions. That is, it has the reverse semantics:
* cap_has_capability() returns 0 when a task has a capability, but the
* kernel's capable() and has_capability() returns 1 for this case.
*/
int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
int cap, int audit)
{
for (;;) {
- /* The owner of the user namespace has all caps. */
- if (targ_ns != &init_user_ns && uid_eq(targ_ns->owner, cred->euid))
- return 0;
+ struct user_namespace *parent_ns;
/* Do we have the necessary capabilities? */
if (targ_ns == cred->user_ns)
return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
/* Have we tried all of the parent namespaces? */
if (targ_ns == &init_user_ns)
return -EPERM;
+ parent_ns = targ_ns->parent;
+
+ /*
+ * The owner of the user namespace in the parent user
+ * namespace has all caps.
+ */
+ if ((parent_ns == cred->user_ns) && uid_eq(targ_ns->owner, cred->euid))
+ return 0;
+
/*
- *If you have a capability in a parent user ns, then you have
+ * If you have a capability in a parent user ns, then you have
* it over all children user namespaces as well.
*/
- targ_ns = targ_ns->parent;
+ targ_ns = parent_ns;
}
/* We never get here */
}
/**
* cap_settime - Determine whether the current process may set the system clock
* @ts: The time to set
* @tz: The timezone to set
*
_______________________________________________
Containers mailing list
Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/containers
