Ian Campbell [Fri, 19 Aug 2011 06:25:00 +0000 (06:25 +0000)]
net: add APIs for manipulating skb page fragments.
The primary aim is to add skb_frag_(ref|unref) in order to remove the use of
bare get/put_page on SKB pages fragments and to isolate users from subsequent
changes to the skb_frag_t data structure.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl> Cc: netdev@vger.kernel.org Signed-off-by: David S. Miller <davem@davemloft.net>
David Howells [Mon, 22 Aug 2011 13:09:36 +0000 (14:09 +0100)]
KEYS: Correctly destroy key payloads when their keytype is removed
unregister_key_type() has code to mark a key as dead and make it unavailable in
one loop and then destroy all those unavailable key payloads in the next loop.
However, the loop to mark keys dead renders the key undetectable to the second
loop by changing the key type pointer also.
Fix this by the following means:
(1) The key code has two garbage collectors: one deletes unreferenced keys and
the other alters keyrings to delete links to old dead, revoked and expired
keys. They can end up holding each other up as both want to scan the key
serial tree under spinlock. Combine these into a single routine.
(2) Move the dead key marking, dead link removal and dead key removal into the
garbage collector as a three phase process running over the three cycles
of the normal garbage collection procedure. This is tracked by the
KEY_GC_REAPING_DEAD_1, _2 and _3 state flags.
unregister_key_type() then just unlinks the key type from the list, wakes
up the garbage collector and waits for the third phase to complete.
(3) Downgrade the key types sem in unregister_key_type() once it has deleted
the key type from the list so that it doesn't block the keyctl() syscall.
(4) Dead keys that cannot be simply removed in the third phase have their
payloads destroyed with the key's semaphore write-locked to prevent
interference by the keyctl() syscall. There should be no in-kernel users
of dead keys of that type by the point of unregistration, though keyctl()
may be holding a reference.
(5) Only perform timer recalculation in the GC if the timer actually expired.
If it didn't, we'll get another cycle when it goes off - and if the key
that actually triggered it has been removed, it's not a problem.
(6) Only garbage collect link if the timer expired or if we're doing dead key
clean up phase 2.
(7) As only key_garbage_collector() is permitted to use rb_erase() on the key
serial tree, it doesn't need to revalidate its cursor after dropping the
spinlock as the node the cursor points to must still exist in the tree.
(8) Drop the spinlock in the GC if there is contention on it or if we need to
reschedule. After dealing with that, get the spinlock again and resume
scanning.
This has been tested in the following ways:
(1) Run the keyutils testsuite against it.
(2) Using the AF_RXRPC and RxKAD modules to test keytype removal:
Load the rxrpc_s key type:
# insmod /tmp/af-rxrpc.ko
# insmod /tmp/rxkad.ko
Create a key (http://people.redhat.com/~dhowells/rxrpc/listen.c):
Link it to a session keyring, preferably one with a higher serial number:
# keyctl link 0x20e36251 @s
Kill the process (the key should remain as it's linked to another place):
# fg
/tmp/listen
^C
Remove the key type:
rmmod rxkad
rmmod af-rxrpc
This can be made a more effective test by altering the following part of
the patch:
if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
/* Make sure everyone revalidates their keys if we marked a
* bunch as being dead and make sure all keyring ex-payloads
* are destroyed.
*/
kdebug("dead sync");
synchronize_rcu();
To call synchronize_rcu() in GC phase 1 instead. That causes that the
keyring's old payload content to hang around longer until it's RCU
destroyed - which usually happens after GC phase 3 is complete. This
allows the destroy_dead_key branch to be tested.
Reported-by: Benjamin Coddington <bcodding@gmail.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
David Howells [Mon, 22 Aug 2011 13:09:28 +0000 (14:09 +0100)]
KEYS: The dead key link reaper should be non-reentrant
The dead key link reaper should be non-reentrant as it relies on global state
to keep track of where it's got to when it returns to the work queue manager to
give it some air.
Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
David Howells [Mon, 22 Aug 2011 13:09:20 +0000 (14:09 +0100)]
KEYS: Make the key reaper non-reentrant
Make the key reaper non-reentrant by sticking it on the appropriate system work
queue when we queue it. This will allow it to have global state and drop
locks. It should probably be non-reentrant already as it may spend a long time
holding the key serial spinlock, and so multiple entrants can spend long
periods of time just sitting there spinning, waiting to get the lock.
Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
David Howells [Mon, 22 Aug 2011 13:09:00 +0000 (14:09 +0100)]
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.
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>
David Howells [Mon, 22 Aug 2011 13:08:51 +0000 (14:08 +0100)]
KEYS: __key_link() should use the RCU deref wrapper for keyring payloads
__key_link() should use the RCU deref wrapper rcu_dereference_locked_keyring()
for accessing keyring payloads rather than calling rcu_dereference_protected()
directly.
Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
projects / karo-tx-linux.git / log