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keys: Move the user and user-session keyrings to the user_namespace

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Move the user and user-session keyrings to the user_namespace struct rather
than pinning them from the user_struct struct.  This prevents these
keyrings from propagating across user-namespaces boundaries with regard to
the KEY_SPEC_* flags, thereby making them more useful in a containerised
environment.

The issue is that a single user_struct may be represent UIDs in several
different namespaces.

The way the patch does this is by attaching a 'register keyring' in each
user_namespace and then sticking the user and user-session keyrings into
that.  It can then be searched to retrieve them.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jann Horn <jannh@google.com>
This commit is contained in:
David Howells
2019-06-26 21:02:32 +01:00
parent b206f281d0
commit 0f44e4d976
9 changed files with 200 additions and 133 deletions
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7
kernel/user.c
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@@ -64,10 +64,7 @@ struct user_namespace init_user_ns = {
.flags = USERNS_INIT_FLAGS,
#ifdef CONFIG_KEYS
.keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
#endif
#ifdef CONFIG_PERSISTENT_KEYRINGS
.persistent_keyring_register_sem =
__RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
.keyring_sem = __RWSEM_INITIALIZER(init_user_ns.keyring_sem),
#endif
};
EXPORT_SYMBOL_GPL(init_user_ns);
@@ -143,8 +140,6 @@ static void free_user(struct user_struct *up, unsigned long flags)
{
uid_hash_remove(up);
spin_unlock_irqrestore(&uidhash_lock, flags);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
}