Commit 012146d0 authored by David Howells's avatar David Howells Committed by James Morris
Browse files

CRED: Fix prepare_kernel_cred() to provide a new thread_group_cred struct

Fix prepare_kernel_cred() to provide a new, separate thread_group_cred struct
otherwise when using request_key() ____call_usermodehelper() calls
umh_keys_init() with the new creds pointing to init_tgcred, which
umh_keys_init() then blithely alters.

The problem can be demonstrated by:

	# keyctl request2 user a debug:a @s
	# grep req /proc/keys
	079906a5 I--Q--     1 perm 1f3f0000     0     0 keyring   _req.249681132: 1/4
	38ef1626 IR----     1 expd 0b010000     0     0 .request_ key:ee1d4ec pid:4371 ci:1

The keyring _req.XXXX should have gone away, but something (init_tgcred) is
pinning it.

That key actually requested can then be removed and a new one created:

	# keyctl unlink 249681132
	1 links removed
	[root@andromeda ~]# grep req /proc/keys
	116cecac IR----     1 expd 0b010000     0     0 .request_ key:eeb4911 pid:4379 ci:1
	36d1cbf8 I--Q--     1 perm 1f3f0000     0     0 keyring   _req.250300689: 1/4

which causes the old _req keyring to go away and a new one to take its place.

This is a consequence of the changes in:

	commit 87966996
	Author: David Howells <>
	Date:   Fri Jun 17 11:25:59 2011 +0100
	KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring


	commit 17f60a7d

	Author: Eric Paris <>
	Date:   Fri Apr 1 17:07:50 2011 -0400
	capabilites: allow the application of capability limits to usermode helpers

After this patch is applied, the _req keyring and the .request_key key are
cleaned up.
Signed-off-by: default avatarDavid Howells <>
cc: Eric Paris <>
Signed-off-by: default avatarJames Morris <>
parent 6d528b08
......@@ -646,6 +646,9 @@ void __init cred_init(void)
struct cred *prepare_kernel_cred(struct task_struct *daemon)
struct thread_group_cred *tgcred;
const struct cred *old;
struct cred *new;
......@@ -653,6 +656,12 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
if (!new)
return NULL;
tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
if (!tgcred) {
kmem_cache_free(cred_jar, new);
return NULL;
kdebug("prepare_kernel_cred() alloc %p", new);
if (daemon)
......@@ -669,8 +678,11 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
new->tgcred = &init_tgcred;
atomic_set(&tgcred->usage, 1);
tgcred->process_keyring = NULL;
tgcred->session_keyring = NULL;
new->tgcred = tgcred;
new->request_key_auth = NULL;
new->thread_keyring = NULL;
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