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>
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index c886a2b..5be6d01 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -1,6 +1,6 @@
-/* process_keys.c: management of a process's keyrings
+/* Management of a process's keyrings
*
- * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004-2005, 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
@@ -23,6 +23,9 @@
/* session keyring create vs join semaphore */
static DEFINE_MUTEX(key_session_mutex);
+/* user keyring creation semaphore */
+static DEFINE_MUTEX(key_user_keyring_mutex);
+
/* the root user's tracking struct */
struct key_user root_key_user = {
.usage = ATOMIC_INIT(3),
@@ -33,78 +36,84 @@
.uid = 0,
};
-/* the root user's UID keyring */
-struct key root_user_keyring = {
- .usage = ATOMIC_INIT(1),
- .serial = 2,
- .type = &key_type_keyring,
- .user = &root_key_user,
- .sem = __RWSEM_INITIALIZER(root_user_keyring.sem),
- .perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
- .flags = 1 << KEY_FLAG_INSTANTIATED,
- .description = "_uid.0",
-#ifdef KEY_DEBUGGING
- .magic = KEY_DEBUG_MAGIC,
-#endif
-};
-
-/* the root user's default session keyring */
-struct key root_session_keyring = {
- .usage = ATOMIC_INIT(1),
- .serial = 1,
- .type = &key_type_keyring,
- .user = &root_key_user,
- .sem = __RWSEM_INITIALIZER(root_session_keyring.sem),
- .perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_ALL,
- .flags = 1 << KEY_FLAG_INSTANTIATED,
- .description = "_uid_ses.0",
-#ifdef KEY_DEBUGGING
- .magic = KEY_DEBUG_MAGIC,
-#endif
-};
-
/*****************************************************************************/
/*
- * allocate the keyrings to be associated with a UID
+ * install user and user session keyrings for a particular UID
*/
-int alloc_uid_keyring(struct user_struct *user,
- struct task_struct *ctx)
+static int install_user_keyrings(struct task_struct *tsk)
{
+ struct user_struct *user = tsk->user;
struct key *uid_keyring, *session_keyring;
char buf[20];
int ret;
- /* concoct a default session keyring */
- sprintf(buf, "_uid_ses.%u", user->uid);
+ kenter("%p{%u}", user, user->uid);
- session_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
- KEY_ALLOC_IN_QUOTA, NULL);
- if (IS_ERR(session_keyring)) {
- ret = PTR_ERR(session_keyring);
- goto error;
+ if (user->uid_keyring) {
+ kleave(" = 0 [exist]");
+ return 0;
}
- /* and a UID specific keyring, pointed to by the default session
- * keyring */
- sprintf(buf, "_uid.%u", user->uid);
-
- uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1, ctx,
- KEY_ALLOC_IN_QUOTA, session_keyring);
- if (IS_ERR(uid_keyring)) {
- key_put(session_keyring);
- ret = PTR_ERR(uid_keyring);
- goto error;
- }
-
- /* install the keyrings */
- user->uid_keyring = uid_keyring;
- user->session_keyring = session_keyring;
+ mutex_lock(&key_user_keyring_mutex);
ret = 0;
-error:
- return ret;
+ if (!user->uid_keyring) {
+ /* get the UID-specific keyring
+ * - there may be one in existence already as it may have been
+ * pinned by a session, but the user_struct pointing to it
+ * may have been destroyed by setuid */
+ sprintf(buf, "_uid.%u", user->uid);
-} /* end alloc_uid_keyring() */
+ uid_keyring = find_keyring_by_name(buf, true);
+ if (IS_ERR(uid_keyring)) {
+ uid_keyring = keyring_alloc(buf, user->uid, (gid_t) -1,
+ tsk, KEY_ALLOC_IN_QUOTA,
+ NULL);
+ if (IS_ERR(uid_keyring)) {
+ ret = PTR_ERR(uid_keyring);
+ goto error;
+ }
+ }
+
+ /* get a default session keyring (which might also exist
+ * already) */
+ sprintf(buf, "_uid_ses.%u", user->uid);
+
+ session_keyring = find_keyring_by_name(buf, true);
+ if (IS_ERR(session_keyring)) {
+ session_keyring =
+ keyring_alloc(buf, user->uid, (gid_t) -1,
+ tsk, KEY_ALLOC_IN_QUOTA, NULL);
+ if (IS_ERR(session_keyring)) {
+ ret = PTR_ERR(session_keyring);
+ goto error_release;
+ }
+
+ /* we install a link from the user session keyring to
+ * the user keyring */
+ ret = key_link(session_keyring, uid_keyring);
+ if (ret < 0)
+ goto error_release_both;
+ }
+
+ /* install the keyrings */
+ user->uid_keyring = uid_keyring;
+ user->session_keyring = session_keyring;
+ }
+
+ mutex_unlock(&key_user_keyring_mutex);
+ kleave(" = 0");
+ return 0;
+
+error_release_both:
+ key_put(session_keyring);
+error_release:
+ key_put(uid_keyring);
+error:
+ mutex_unlock(&key_user_keyring_mutex);
+ kleave(" = %d", ret);
+ return ret;
+}
/*****************************************************************************/
/*
@@ -481,7 +490,7 @@
}
}
/* or search the user-session keyring */
- else {
+ else if (context->user->session_keyring) {
key_ref = keyring_search_aux(
make_key_ref(context->user->session_keyring, 1),
context, type, description, match);
@@ -614,6 +623,9 @@
if (!context->signal->session_keyring) {
/* always install a session keyring upon access if one
* doesn't exist yet */
+ ret = install_user_keyrings(context);
+ if (ret < 0)
+ goto error;
ret = install_session_keyring(
context, context->user->session_keyring);
if (ret < 0)
@@ -628,12 +640,24 @@
break;
case KEY_SPEC_USER_KEYRING:
+ if (!context->user->uid_keyring) {
+ ret = install_user_keyrings(context);
+ if (ret < 0)
+ goto error;
+ }
+
key = context->user->uid_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_USER_SESSION_KEYRING:
+ if (!context->user->session_keyring) {
+ ret = install_user_keyrings(context);
+ if (ret < 0)
+ goto error;
+ }
+
key = context->user->session_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
@@ -744,7 +768,7 @@
mutex_lock(&key_session_mutex);
/* look for an existing keyring of this name */
- keyring = find_keyring_by_name(name, 0);
+ keyring = find_keyring_by_name(name, false);
if (PTR_ERR(keyring) == -ENOKEY) {
/* not found - try and create a new one */
keyring = keyring_alloc(name, tsk->uid, tsk->gid, tsk,