• David Howells's avatar
    CRED: Fix prepare_kernel_cred() to provide a new thread_group_cred struct · 012146d0
    David Howells authored
    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 87966996
    	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 17f60a7d
    
    
    	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: default avatarDavid Howells <dhowells@redhat.com>
    cc: Eric Paris <eparis@redhat.com>
    Signed-off-by: default avatarJames Morris <jmorris@namei.org>
    012146d0