keys: don't generate user and user session keyrings unless they're accessed

Don't generate the per-UID user and user session keyrings unless they're
explicitly accessed.  This solves a problem during a login process whereby
set*uid() is called before the SELinux PAM module, resulting in the per-UID
keyrings having the wrong security labels.

This also cures the problem of multiple per-UID keyrings sometimes appearing
due to PAM modules (including pam_keyinit) setuiding and causing user_structs
to come into and go out of existence whilst the session keyring pins the user
keyring.  This is achieved by first searching for extant per-UID keyrings
before inventing new ones.

The serial bound argument is also dropped from find_keyring_by_name() as it's
not currently made use of (setting it to 0 disables the feature).

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: <kwc@citi.umich.edu>
Cc: <arunsr@cse.iitk.ac.in>
Cc: <dwalsh@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 8 deletions

diff --git a/include/linux/key.h b/include/linux/key.h
index 8b0bd3393abc..2effd031a817 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -268,9 +268,6 @@ extern struct key *key_lookup(key_serial_t id);
 /*
  * the userspace interface
  */
-extern struct key root_user_keyring, root_session_keyring;
-extern int alloc_uid_keyring(struct user_struct *user,
-                             struct task_struct *ctx);
 extern void switch_uid_keyring(struct user_struct *new_user);
 extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
 extern int copy_thread_group_keys(struct task_struct *tsk);
@@ -299,7 +296,6 @@ extern void key_init(void);
 #define make_key_ref(k, p)                      ({ NULL; })
 #define key_ref_to_ptr(k)               ({ NULL; })
 #define is_key_possessed(k)             0
-#define alloc_uid_keyring(u,c)          0
 #define switch_uid_keyring(u)           do { } while(0)
 #define __install_session_keyring(t, k) ({ NULL; })
 #define copy_keys(f,t)                  0
@@ -312,10 +308,6 @@ extern void key_init(void);
 #define key_fsgid_changed(t)            do { } while(0)
 #define key_init()                      do { } while(0)
 
-/* Initial keyrings */
-extern struct key root_user_keyring;
-extern struct key root_session_keyring;
-
 #endif /* CONFIG_KEYS */
 #endif /* __KERNEL__ */
 #endif /* _LINUX_KEY_H */