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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
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19
security/keys/keyring.c
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@@ -1,6 +1,6 @@
/* keyring.c: keyring handling
/* Keyring handling
*
* 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
@@ -79,7 +79,7 @@ static DECLARE_RWSEM(keyring_serialise_link_sem);
* publish the name of a keyring so that it can be found by name (if it has
* one)
*/
void keyring_publish_name(struct key *keyring)
static void keyring_publish_name(struct key *keyring)
{
int bucket;
@@ -516,10 +516,9 @@ key_ref_t __keyring_search_one(key_ref_t keyring_ref,
/*
* find a keyring with the specified name
* - all named keyrings are searched
* - only find keyrings with search permission for the process
* - only find keyrings with a serial number greater than the one specified
* - normally only finds keyrings with search permission for the current process
*/
struct key *find_keyring_by_name(const char *name, key_serial_t bound)
struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
{
struct key *keyring;
int bucket;
@@ -545,15 +544,11 @@ struct key *find_keyring_by_name(const char *name, key_serial_t bound)
if (strcmp(keyring->description, name) != 0)
continue;
if (key_permission(make_key_ref(keyring, 0),
if (!skip_perm_check &&
key_permission(make_key_ref(keyring, 0),
KEY_SEARCH) < 0)
continue;
/* found a potential candidate, but we still need to
* check the serial number */
if (keyring->serial <= bound)
continue;
/* we've got a match */
atomic_inc(&keyring->usage);
read_unlock(&keyring_name_lock);