[PATCH 07/43] cred: Refcount the user_ns pointed to by the cred.

"Eric W. Beiderman
2012-04-08T05:21:09Z

From: Eric W. Biederman <ebiederm@xmission.com>

struct user_struct will shortly loose it's user_ns reference
so make the cred user_ns reference a proper reference complete
with reference counting.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
include/linux/cred.h | 2 +-
kernel/cred.c | 8 +++-----
kernel/user_namespace.c | 8 +++++---
security/keys/process_keys.c | 2 +-
4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/linux/cred.h b/include/linux/cred.h
index d12c4e4..2c60ec8 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -146,7 +146,7 @@ struct cred {
void *security; /* subjective LSM security */
#endif
struct user_struct *user; /* real user ID subscription */
- struct user_namespace *user_ns; /* cached user->user_ns */
+ struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
struct group_info *group_info; /* supplementary groups for euid/fsgid */
struct rcu_head rcu; /* RCU deletion hook */
};
diff --git a/kernel/cred.c b/kernel/cred.c
index 97b36ee..7a0d806 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -148,6 +148,7 @@ static void put_cred_rcu(struct rcu_head *rcu)
if (cred->group_info)
put_group_info(cred->group_info);
free_uid(cred->user);
+ put_user_ns(cred->user_ns);
kmem_cache_free(cred_jar, cred);
}

@@ -303,6 +304,7 @@ struct cred *prepare_creds(void)
set_cred_subscribers(new, 0);
get_group_info(new->group_info);
get_uid(new->user);
+ get_user_ns(new->user_ns);

#ifdef CONFIG_KEYS
key_get(new->thread_keyring);
@@ -412,11 +414,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
goto error_put;
}

- /* cache user_ns in cred. Doesn't need a refcount because it will
- * stay pinned by cred->user
- */
- new->user_ns = new->user->user_ns;
-
#ifdef CONFIG_KEYS
/* new threads get their own thread keyrings if their parent already
* had one */
@@ -676,6 +673,7 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
atomic_set(&new->usage, 1);
set_cred_subscribers(new, 0);
get_uid(new->user);
+ get_user_ns(new->user_ns);
get_group_info(new->group_info);

#ifdef CONFIG_KEYS
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index f084083..58bb878 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -24,7 +24,7 @@ static struct kmem_cache *user_ns_cachep __read_mostly;
*/
int create_user_ns(struct cred *new)
{
- struct user_namespace *ns;
+ struct user_namespace *ns, *parent_ns = new->user_ns;
struct user_struct *root_user;
int n;

@@ -57,8 +57,10 @@ int create_user_ns(struct cred *new)
#endif
/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */

- /* root_user holds a reference to ns, our reference can be dropped */
- put_user_ns(ns);
+ /* Leave the reference to our user_ns with the new cred */
+ new->user_ns = ns;
+
+ put_user_ns(parent_ns);

return 0;
}
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 70febff..447fb76 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -858,7 +858,7 @@ void key_replace_session_keyring(void)
new-> sgid = old-> sgid;
new->fsgid = old->fsgid;
new->user = get_uid(old->user);
- new->user_ns = new->user_ns;
+ new->user_ns = get_user_ns(new->user_ns);
new->group_info = get_group_info(old->group_info);

new->securebits = old->securebits;
--
1.7.2.5