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

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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>
This commit is contained in:
David Howells 2008-04-29 01:01:31 -07:00 • committed by Linus Torvalds
parent 6b79ccb514
commit 69664cf16a
7 changed files with 99 additions and 148 deletions
Download patch file Download diff file Expand all files Collapse all files

15
kernel/user.c
View file

@ -53,10 +53,6 @@ struct user_struct root_user = {
.files = ATOMIC_INIT(0),
.sigpending = ATOMIC_INIT(0),
.locked_shm = 0,
#ifdef CONFIG_KEYS
.uid_keyring = &root_user_keyring,
.session_keyring = &root_session_keyring,
#endif
#ifdef CONFIG_USER_SCHED
.tg = &init_task_group,
#endif
@ -420,12 +416,12 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
new->mq_bytes = 0;
#endif
new->locked_shm = 0;
if (alloc_uid_keyring(new, current) < 0)
goto out_free_user;
#ifdef CONFIG_KEYS
new->uid_keyring = new->session_keyring = NULL;
#endif
if (sched_create_user(new) < 0)
goto out_put_keys;
goto out_free_user;
if (uids_user_create(new))
goto out_destoy_sched;
@ -459,9 +455,6 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
out_destoy_sched:
sched_destroy_user(new);
out_put_keys:
key_put(new->uid_keyring);
key_put(new->session_keyring);
out_free_user:
kmem_cache_free(uid_cachep, new);
out_unlock: