Pull security subsystem updates from James Morris:
"A quiet cycle for the security subsystem with just a few maintenance
updates."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
Smack: create a sysfs mount point for smackfs
Smack: use select not depends in Kconfig
Yama: remove locking from delete path
Yama: add RCU to drop read locking
drivers/char/tpm: remove tasklet and cleanup
KEYS: Use keyring_alloc() to create special keyrings
KEYS: Reduce initial permissions on keys
KEYS: Make the session and process keyrings per-thread
seccomp: Make syscall skipping and nr changes more consistent
key: Fix resource leak
keys: Fix unreachable code
KEYS: Add payload preparsing opportunity prior to key instantiate or update
Reduce the initial permissions on new keys to grant the possessor everything,
view permission only to the user (so the keys can be seen in /proc/keys) and
nothing else.
This gives the creator a chance to adjust the permissions mask before other
processes can access the new key or create a link to it.
To aid with this, keyring_alloc() now takes a permission argument rather than
setting the permissions itself.
The following permissions are now set:
(1) The user and user-session keyrings grant the user that owns them full
permissions and grant a possessor everything bar SETATTR.
(2) The process and thread keyrings grant the possessor full permissions but
only grant the user VIEW. This permits the user to see them in
/proc/keys, but not to do anything with them.
(3) Anonymous session keyrings grant the possessor full permissions, but only
grant the user VIEW and READ. This means that the user can see them in
/proc/keys and can list them, but nothing else. Possibly READ shouldn't
be provided either.
(4) Named session keyrings grant everything an anonymous session keyring does,
plus they grant the user LINK permission. The whole point of named
session keyrings is that others can also subscribe to them. Possibly this
should be a separate permission to LINK.
(5) The temporary session keyring created by call_sbin_request_key() gets the
same permissions as an anonymous session keyring.
(6) Keys created by add_key() get VIEW, SEARCH, LINK and SETATTR for the
possessor, plus READ and/or WRITE if the key type supports them. The used
only gets VIEW now.
(7) Keys created by request_key() now get the same as those created by
add_key().
Reported-by: Lennart Poettering <lennart@poettering.net>
Reported-by: Stef Walter <stefw@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Make the session keyring per-thread rather than per-process, but still
inherited from the parent thread to solve a problem with PAM and gdm.
The problem is that join_session_keyring() will reject attempts to change the
session keyring of a multithreaded program but gdm is now multithreaded before
it gets to the point of starting PAM and running pam_keyinit to create the
session keyring. See:
https://bugs.freedesktop.org/show_bug.cgi?id=49211
The reason that join_session_keyring() will only change the session keyring
under a single-threaded environment is that it's hard to alter the other
thread's credentials to effect the change in a multi-threaded program. The
problems are such as:
(1) How to prevent two threads both running join_session_keyring() from
racing.
(2) Another thread's credentials may not be modified directly by this process.
(3) The number of threads is uncertain whilst we're not holding the
appropriate spinlock, making preallocation slightly tricky.
(4) We could use TIF_NOTIFY_RESUME and key_replace_session_keyring() to get
another thread to replace its keyring, but that means preallocating for
each thread.
A reasonable way around this is to make the session keyring per-thread rather
than per-process and just document that if you want a common session keyring,
you must get it before you spawn any threads - which is the current situation
anyway.
Whilst we're at it, we can the process keyring behave in the same way. This
means we can clean up some of the ickyness in the creds code.
Basically, after this patch, the session, process and thread keyrings are about
inheritance rules only and not about sharing changes of keyring.
Reported-by: Mantas M. <grawity@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Ray Strode <rstrode@redhat.com>
- Replace key_user ->user_ns equality checks with kuid_has_mapping checks.
- Use from_kuid to generate key descriptions
- Use kuid_t and kgid_t and the associated helpers instead of uid_t and gid_t
- Avoid potential problems with file descriptor passing by displaying
keys in the user namespace of the opener of key status proc files.
Cc: linux-security-module@vger.kernel.org
Cc: keyrings@linux-nfs.org
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Fix error handling in construct_key_and_link().
If construct_alloc_key() returns an error, it shouldn't pass out through
the normal path as the key_serial() called by the kleave() statement
will oops when it gets an error code in the pointer:
BUG: unable to handle kernel paging request at ffffffffffffff84
IP: [<ffffffff8120b401>] request_key_and_link+0x4d7/0x52f
..
Call Trace:
[<ffffffff8120b52c>] request_key+0x41/0x75
[<ffffffffa00ed6e8>] cifs_get_spnego_key+0x206/0x226 [cifs]
[<ffffffffa00eb0c9>] CIFS_SessSetup+0x511/0x1234 [cifs]
[<ffffffffa00d9799>] cifs_setup_session+0x90/0x1ae [cifs]
[<ffffffffa00d9c02>] cifs_get_smb_ses+0x34b/0x40f [cifs]
[<ffffffffa00d9e05>] cifs_mount+0x13f/0x504 [cifs]
[<ffffffffa00caabb>] cifs_do_mount+0xc4/0x672 [cifs]
[<ffffffff8113ae8c>] mount_fs+0x69/0x155
[<ffffffff8114ff0e>] vfs_kern_mount+0x63/0xa0
[<ffffffff81150be2>] do_kern_mount+0x4d/0xdf
[<ffffffff81152278>] do_mount+0x63c/0x69f
[<ffffffff8115255c>] sys_mount+0x88/0xc2
[<ffffffff814fbdc2>] system_call_fastpath+0x16/0x1b
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
____call_usermodehelper() now erases any credentials set by the
subprocess_inf::init() function. The problem is that commit
17f60a7da1 ("capabilites: allow the application of capability limits
to usermode helpers") creates and commits new credentials with
prepare_kernel_cred() after the call to the init() function. This wipes
all keyrings after umh_keys_init() is called.
The best way to deal with this is to put the init() call just prior to
the commit_creds() call, and pass the cred pointer to init(). That
means that umh_keys_init() and suchlike can modify the credentials
_before_ they are published and potentially in use by the rest of the
system.
This prevents request_key() from working as it is prevented from passing
the session keyring it set up with the authorisation token to
/sbin/request-key, and so the latter can't assume the authority to
instantiate the key. This causes the in-kernel DNS resolver to fail
with ENOKEY unconditionally.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Tested-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* 'docs-move' of git://git.kernel.org/pub/scm/linux/kernel/git/rdunlap/linux-docs:
Create Documentation/security/, move LSM-, credentials-, and keys-related files from Documentation/ to Documentation/security/, add Documentation/security/00-INDEX, and update all occurrences of Documentation/<moved_file> to Documentation/security/<moved_file>.
move LSM-, credentials-, and keys-related files from Documentation/
to Documentation/security/,
add Documentation/security/00-INDEX, and
update all occurrences of Documentation/<moved_file>
to Documentation/security/<moved_file>.
Improve /proc/keys by:
(1) Don't attempt to summarise the payload of a negated key. It won't have
one. To this end, a helper function - key_is_instantiated() has been
added that allows the caller to find out whether the key is positively
instantiated (as opposed to being uninstantiated or negatively
instantiated).
(2) Do show keys that are negative, expired or revoked rather than hiding
them. This requires an override flag (no_state_check) to be passed to
search_my_process_keyrings() and keyring_search_aux() to suppress this
check.
Without this, keys that are possessed by the caller, but only grant
permissions to the caller if possessed are skipped as the possession check
fails.
Keys that are visible due to user, group or other checks are visible with
or without this patch.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Add a new keyctl op to reject a key with a specified error code. This works
much the same as negating a key, and so keyctl_negate_key() is made a special
case of keyctl_reject_key(). The difference is that keyctl_negate_key()
selects ENOKEY as the error to be reported.
Typically the key would be rejected with EKEYEXPIRED, EKEYREVOKED or
EKEYREJECTED, but this is not mandatory.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Fix __key_link_end()'s attempt to fix up the quota if an error occurs.
There are two erroneous cases: Firstly, we always decrease the quota if
the preallocated replacement keyring needs cleaning up, irrespective of
whether or not we should (we may have replaced a pointer rather than
adding another pointer).
Secondly, we never clean up the quota if we added a pointer without the
keyring storage being extended (we allocate multiple pointers at a time,
even if we're not going to use them all immediately).
We handle this by setting the bottom bit of the preallocation pointer in
__key_link_begin() to indicate that the quota needs fixing up, which is
then passed to __key_link() (which clears the whole thing) and
__key_link_end().
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In construct_alloc_key(), up_write() is called in the error path if
__key_link_begin() fails, but this is incorrect as __key_link_begin() only
returns with the nominated keyring locked if it returns successfully.
Without this patch, you might see the following in dmesg:
=====================================
[ BUG: bad unlock balance detected! ]
-------------------------------------
mount.cifs/5769 is trying to release lock (&key->sem) at:
[<ffffffff81201159>] request_key_and_link+0x263/0x3fc
but there are no more locks to release!
other info that might help us debug this:
3 locks held by mount.cifs/5769:
#0: (&type->s_umount_key#41/1){+.+.+.}, at: [<ffffffff81131321>] sget+0x278/0x3e7
#1: (&ret_buf->session_mutex){+.+.+.}, at: [<ffffffffa0258e59>] cifs_get_smb_ses+0x35a/0x443 [cifs]
#2: (root_key_user.cons_lock){+.+.+.}, at: [<ffffffff81201000>] request_key_and_link+0x10a/0x3fc
stack backtrace:
Pid: 5769, comm: mount.cifs Not tainted 2.6.37-rc6+ #1
Call Trace:
[<ffffffff81201159>] ? request_key_and_link+0x263/0x3fc
[<ffffffff81081601>] print_unlock_inbalance_bug+0xca/0xd5
[<ffffffff81083248>] lock_release_non_nested+0xc1/0x263
[<ffffffff81201159>] ? request_key_and_link+0x263/0x3fc
[<ffffffff81201159>] ? request_key_and_link+0x263/0x3fc
[<ffffffff81083567>] lock_release+0x17d/0x1a4
[<ffffffff81073f45>] up_write+0x23/0x3b
[<ffffffff81201159>] request_key_and_link+0x263/0x3fc
[<ffffffffa026fe9e>] ? cifs_get_spnego_key+0x61/0x21f [cifs]
[<ffffffff812013c5>] request_key+0x41/0x74
[<ffffffffa027003d>] cifs_get_spnego_key+0x200/0x21f [cifs]
[<ffffffffa026e296>] CIFS_SessSetup+0x55d/0x1273 [cifs]
[<ffffffffa02589e1>] cifs_setup_session+0x90/0x1ae [cifs]
[<ffffffffa0258e7e>] cifs_get_smb_ses+0x37f/0x443 [cifs]
[<ffffffffa025a9e3>] cifs_mount+0x1aa1/0x23f3 [cifs]
[<ffffffff8111fd94>] ? alloc_debug_processing+0xdb/0x120
[<ffffffffa027002c>] ? cifs_get_spnego_key+0x1ef/0x21f [cifs]
[<ffffffffa024cc71>] cifs_do_mount+0x165/0x2b3 [cifs]
[<ffffffff81130e72>] vfs_kern_mount+0xaf/0x1dc
[<ffffffff81131007>] do_kern_mount+0x4d/0xef
[<ffffffff811483b9>] do_mount+0x6f4/0x733
[<ffffffff8114861f>] sys_mount+0x88/0xc2
[<ffffffff8100ac42>] system_call_fastpath+0x16/0x1b
Reported-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-and-Tested-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
request_key() should return -ENOKEY if the key it constructs has been
negatively instantiated.
Without this, request_key() can return an unusable key to its caller,
and if the caller then does key_validate() that won't catch the problem.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In commit bb952bb98a there was the accidental
deletion of a statement from call_sbin_request_key() to render the process
keyring ID to a text string so that it can be passed to /sbin/request-key.
With gcc 4.6.0 this causes the following warning:
CC security/keys/request_key.o
security/keys/request_key.c: In function 'call_sbin_request_key':
security/keys/request_key.c:102:15: warning: variable 'prkey' set but not used
This patch reinstates that statement.
Without this statement, /sbin/request-key will get some random rubbish from the
stack as that parameter.
Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
call_usermodehelper_keys() uses call_usermodehelper_setkeys() to change
subprocess_info->cred in advance. Now that we have info->init() we can
change this code to set tgcred->session_keyring in context of execing
kernel thread.
Note: since currently call_usermodehelper_keys() is never called with
UMH_NO_WAIT, call_usermodehelper_keys()->key_get() and umh_keys_cleanup()
are not really needed, we could rely on install_session_keyring_to_cred()
which does key_get() on success.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Do preallocation for __key_link() so that the various callers in request_key.c
can deal with any errors from this source before attempting to construct a key.
This allows them to assume that the actual linkage step is guaranteed to be
successful.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Errors from construct_alloc_key() shouldn't just be ignored in the way they are
by construct_key_and_link(). The only error that can be ignored so is
EINPROGRESS as that is used to indicate that we've found a key and don't need
to construct one.
We don't, however, handle ENOMEM, EDQUOT or EACCES to indicate allocation
failures of one sort or another.
Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
call_sbin_request_key() creates a keyring and then attempts to insert a link to
the authorisation key into that keyring, but does so without holding a write
lock on the keyring semaphore.
It will normally get away with this because it hasn't told anyone that the
keyring exists yet. The new keyring, however, has had its serial number
published, which means it can be accessed directly by that handle.
This was found by a previous patch that adds RCU lockdep checks to the code
that reads the keyring payload pointer, which includes a check that the keyring
semaphore is actually locked.
Without this patch, the following command:
keyctl request2 user b a @s
will provoke the following lockdep warning is displayed in dmesg:
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
security/keys/keyring.c:727 invoked rcu_dereference_check() without protection!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
2 locks held by keyctl/2076:
#0: (key_types_sem){.+.+.+}, at: [<ffffffff811a5b29>] key_type_lookup+0x1c/0x71
#1: (keyring_serialise_link_sem){+.+.+.}, at: [<ffffffff811a6d1e>] __key_link+0x4d/0x3c5
stack backtrace:
Pid: 2076, comm: keyctl Not tainted 2.6.34-rc6-cachefs #54
Call Trace:
[<ffffffff81051fdc>] lockdep_rcu_dereference+0xaa/0xb2
[<ffffffff811a6d1e>] ? __key_link+0x4d/0x3c5
[<ffffffff811a6e6f>] __key_link+0x19e/0x3c5
[<ffffffff811a5952>] ? __key_instantiate_and_link+0xb1/0xdc
[<ffffffff811a59bf>] ? key_instantiate_and_link+0x42/0x5f
[<ffffffff811aa0dc>] call_sbin_request_key+0xe7/0x33b
[<ffffffff8139376a>] ? mutex_unlock+0x9/0xb
[<ffffffff811a5952>] ? __key_instantiate_and_link+0xb1/0xdc
[<ffffffff811a59bf>] ? key_instantiate_and_link+0x42/0x5f
[<ffffffff811aa6fa>] ? request_key_auth_new+0x1c2/0x23c
[<ffffffff810aaf15>] ? cache_alloc_debugcheck_after+0x108/0x173
[<ffffffff811a9d00>] ? request_key_and_link+0x146/0x300
[<ffffffff810ac568>] ? kmem_cache_alloc+0xe1/0x118
[<ffffffff811a9e45>] request_key_and_link+0x28b/0x300
[<ffffffff811a89ac>] sys_request_key+0xf7/0x14a
[<ffffffff81052c0b>] ? trace_hardirqs_on_caller+0x10c/0x130
[<ffffffff81394fb9>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[<ffffffff81001eeb>] system_call_fastpath+0x16/0x1b
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
The request_key() system call and request_key_and_link() should make a
link from an existing key to the destination keyring (if supplied), not
just from a new key to the destination keyring.
This can be tested by:
ring=`keyctl newring fred @s`
keyctl request2 user debug:a a
keyctl request user debug:a $ring
keyctl list $ring
If it says:
keyring is empty
then it didn't work. If it shows something like:
1 key in keyring:
1070462727: --alswrv 0 0 user: debug:a
then it did.
request_key() system call is meant to recursively search all your keyrings for
the key you desire, and, optionally, if it doesn't exist, call out to userspace
to create one for you.
If request_key() finds or creates a key, it should, optionally, create a link
to that key from the destination keyring specified.
Therefore, if, after a successful call to request_key() with a desination
keyring specified, you see the destination keyring empty, the code didn't work
correctly.
If you see the found key in the keyring, then it did - which is what the patch
is required for.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the following RCU warning:
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
security/keys/request_key.c:116 invoked rcu_dereference_check() without protection!
This was caused by doing:
[root@andromeda ~]# keyctl newring fred @s
539196288
[root@andromeda ~]# keyctl request2 user a a 539196288
request_key: Required key not available
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
