keys: Include target namespace in match criteria

Currently a key has a standard matching criteria of { type, description }
and this is used to only allow keys with unique criteria in a keyring.
This means, however, that you cannot have keys with the same type and
description but a different target namespace in the same keyring.

This is a potential problem for a containerised environment where, say, a
container is made up of some parts of its mount space involving netfs
superblocks from two different network namespaces.

This is also a problem for shared system management keyrings such as the
DNS records keyring or the NFS idmapper keyring that might contain keys
from different network namespaces.

Fix this by including a namespace component in a key's matching criteria.
Keyring types are marked to indicate which, if any, namespace is relevant
to keys of that type, and that namespace is set when the key is created
from the current task's namespace set.

The capability bit KEYCTL_CAPS1_NS_KEY_TAG is set if the kernel is
employing this feature.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/key.h b/include/linux/key.h
index ae1177302d70..abc68555bac3 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -82,9 +82,16 @@ struct cred;
 
 struct key_type;
 struct key_owner;
+struct key_tag;
 struct keyring_list;
 struct keyring_name;
 
+struct key_tag {
+	struct rcu_head		rcu;
+	refcount_t		usage;
+	bool			removed;	/* T when subject removed */
+};
+
 struct keyring_index_key {
 	/* [!] If this structure is altered, the union in struct key must change too! */
 	unsigned long		hash;			/* Hash value */
@@ -101,6 +108,7 @@ struct keyring_index_key {
 		unsigned long x;
 	};
 	struct key_type		*type;
+	struct key_tag		*domain_tag;	/* Domain of operation */
 	const char		*description;
 };
 
@@ -218,6 +226,7 @@ struct key {
 			unsigned long	hash;
 			unsigned long	len_desc;
 			struct key_type	*type;		/* type of key */
+			struct key_tag	*domain_tag;	/* Domain of operation */
 			char		*description;
 		};
 	};
@@ -268,6 +277,7 @@ extern struct key *key_alloc(struct key_type *type,
 extern void key_revoke(struct key *key);
 extern void key_invalidate(struct key *key);
 extern void key_put(struct key *key);
+extern bool key_put_tag(struct key_tag *tag);
 
 static inline struct key *__key_get(struct key *key)
 {