From: David Howells Date: Mon, 22 Aug 2011 13:09:00 +0000 (+0100) Subject: CRED: Fix prepare_kernel_cred() to provide a new thread_group_cred struct X-Git-Tag: next-20110823~26^2~4 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=012146d0728f85f7a5c7c36fb84bba33e2760507;p=karo-tx-linux.git 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 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 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 cc: Eric Paris Signed-off-by: James Morris --- 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;