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author | David Howells <dhowells@redhat.com> | 2011-08-22 14:09:00 +0100 |
---|---|---|
committer | James Morris <jmorris@namei.org> | 2011-08-23 09:57:35 +1000 |
commit | 012146d0728f85f7a5c7c36fb84bba33e2760507 (patch) | |
tree | 215ad5926013e6a71d1ea750a81596fa20028dcc /kernel/cred.c | |
parent | 6d528b082294f0ddabd6368297546a2c0b67d4fe (diff) | |
download | lwn-012146d0728f85f7a5c7c36fb84bba33e2760507.tar.gz lwn-012146d0728f85f7a5c7c36fb84bba33e2760507.zip |
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
249681132
# 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 879669961b11e7f40b518784863a259f735a72bf
Author: David Howells <dhowells@redhat.com>
Date: Fri Jun 17 11:25:59 2011 +0100
KEYS/DNS: Fix ____call_usermodehelper() to not lose the session keyring
and:
commit 17f60a7da150fdd0cfb9756f86a262daa72c835f
Author: Eric Paris <eparis@redhat.com>
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: David Howells <dhowells@redhat.com>
cc: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'kernel/cred.c')
-rw-r--r-- | kernel/cred.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/cred.c b/kernel/cred.c index 174fa84eca30..f1e22556bc49 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -646,6 +646,9 @@ void __init cred_init(void) */ struct cred *prepare_kernel_cred(struct task_struct *daemon) { +#ifdef CONFIG_KEYS + struct thread_group_cred *tgcred; +#endif 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) get_group_info(new->group_info); #ifdef CONFIG_KEYS - atomic_inc(&init_tgcred.usage); - new->tgcred = &init_tgcred; + atomic_set(&tgcred->usage, 1); + spin_lock_init(&tgcred->lock); + tgcred->process_keyring = NULL; + tgcred->session_keyring = NULL; + new->tgcred = tgcred; new->request_key_auth = NULL; new->thread_keyring = NULL; new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; |