Up to now, key manipulation is supposed to run under RTNL to
avoid concurrent manipulations and also allow the set_key()
hardware callback to sleep. This is not feasible because STA
structs are rcu-protected and thus a lot of operations there
cannot take the RTNL. Also, key references are rcu-protected
so we cannot do things atomically.
This patch changes key locking completely:
* key operations are now atomic
* hardware crypto offload is enabled and disabled from
a workqueue, due to that key freeing is also delayed
* debugfs code is also run from a workqueue
* keys reference STAs (and vice versa!) so during STA
unlink the STAs key reference is removed but not the
keys STA reference, to avoid races key todo work is
run before STA destruction.
* fewer STA operations now need the RTNL which was
required due to key operations
This fixes the locking problems lockdep pointed out and also
makes things more light-weight because the rtnl isn't required
as much.
Note that the key todo lock/key mutex are global locks, this
is not required, of course, they could be per-hardware instead.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
When the IBSS code tries to flush the STA list, it does so in
an atomic context. Flushing isn't safe there, however, and
requires the RTNL, so we need to defer it to a workqueue.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Today I hit one of my new WARN_ONs in the mac80211 code because
a key wasn't being freed correctly. After wondering for a while
I finally tracked it to the fact that STA keys aren't added to
the per-sdata key list correctly, they are supposed to always be
on that list, not just for default keys. This patch fixes that.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Quite a while ago I started this book. The required kernel-doc
patches have since gone into the tree so it is now possible to
build the book in mainline.
The actual documentation is still rather incomplete and not all
things are linked into the book, but this enables us to edit
the documentation collaboratively, hopefully driver authors can
add documentation based on their experience with mac80211.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This makes access to the STA hash table/list use RCU to protect
against freeing of items. However, it's not a true RCU, the
copy step is missing: whenever somebody changes a STA item it
is simply updated. This is an existing race condition that is
now somewhat understandable.
This patch also fixes the race key freeing vs. STA destruction
by making sure that sta_info_destroy() is always called under
RTNL and frees the key.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Even though I thought about it a lot and had also tested it, some
of my recent changes in the key code broke replacing keys, making
the kernel oops because a key is removed from a list while not on
it.
This patch fixes that using the list as an indication whether or
not the key is on it (an empty list means it's not on any list.)
Also, this patch fixes hw accel enabling, the check for not doing
hw accel when the interface is down was lost and is restored by
this.
Additionally, move adding the key to the list into the function
__ieee80211_key_replace() for more consistency.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
In order to RCU-ify sta_info, we need to be able to allocate
a key without linking it to an sdata/sta structure (because
allocation cannot be done in an rcu critical section). This
patch splits up ieee80211_key_alloc() and updates all users
appropriately.
While at it, this patch fixes a number of race conditions
such as finally making key replacement atomic, unfortunately
at the expense of more complex code.
Note that this patch documents /existing/ bugs with sta info
and key interaction, there is currently a race condition
when a sta info is freed without holding the RTNL. This will
finally be fixed by a followup patch.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Drivers that support mixed AP/STA operation may well need to
know the type of a virtual interface when iterating over them.
The easiest way to support that is to move the interface type
variable into the vif structure.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This "algorithm" is used only internally and is not useful.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Michael Buesch <mb@bu3sch.de>
Acked-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The typedef is not required, we can just use "enum ieee80211_key_alg"
instead of "ieee80211_key_alg"
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This patch makes the mac80211/driver interface rely only on the
IEEE80211_TXCTL_DO_NOT_ENCRYPT flag to signal to the driver whether
a frame should be encrypted or not, since mac80211 internally no
longer relies on HW_KEY_IDX_INVALID either this removes it, changes
the key index to be a u8 in all places and makes the full range of
the value available to drivers.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
No existing drivers use this callback, hence there's no telling
how it might be used. In fact, it is unlikely to be of much use
as-is because the default key index isn't something that the
driver can do much with without knowing which interface it was
for etc. And if it needs the key index for the transmitted frame,
it can get it by keeping a reference to the key_conf structure
and looking it up by hw_key_idx.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
During receive processing, we select the key long before using it and
because there's no locking it is possible that we kfree() the key
after having selected it but before using it for crypto operations.
Obviously, this is bad.
Secondly, during transmit processing, there are two possible races: We
have a similar race between select_key() and using it for encryption,
but we also have a race here between select_key() and hardware
encryption (both when a key is removed.)
This patch solves these issues by using RCU: when a key is to be freed,
we first remove the pointer from the appropriate places (sdata->keys,
sdata->default_key, sta->key) using rcu_assign_pointer() and then
synchronize_rcu(). Then, we can safely kfree() the key and remove it
from the hardware. There's a window here where the hardware may still
be using it for decryption, but we can't work around that without having
two hardware callbacks, one to disable the key for RX and one to disable
it for TX; but the worst thing that will happen is that we receive a
packet decrypted that we don't find a key for any more and then drop it.
When we add a key, we first need to upload it to the hardware and then,
using rcu_assign_pointer() again, link it into our structures.
In the code using keys (TX/RX paths) we use rcu_dereference() to get the
key and enclose the whole tx/rx section in a rcu_read_lock() ...
rcu_read_unlock() block. Because we've uploaded the key to hardware
before linking it into internal structures, we can guarantee that it is
valid once get to into tx().
One possible race condition remains, however: when we have hardware
acceleration enabled and the driver shuts down the queues, we end up
queueing the frame. If now somebody removes the key, the key will be
removed from hwaccel and then then driver will be asked to encrypt the
frame with a key index that has been removed. Hence, drivers will need
to be aware that the hw_key_index they are passed might not be under
all circumstances. Most drivers will, however, simply ignore that
condition and encrypt the frame with the selected key anyway, this
only results in a frame being encrypted with a wrong key or dropped
(rightfully) because the key was not valid. There isn't much we can
do about it unless we want to walk the pending frame queue every time
a key is removed and remove all frames that used it.
This race condition, however, will most likely be solved once we add
multiqueue support to mac80211 because then frames will be queued
further up the stack instead of after being processed.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This moves all the key handling code out from ieee80211_ioctl.c
into key.c and also does the following changes including documentation
updates in mac80211.h:
1) Turn off hardware acceleration for keys when the interface
is down. This is necessary because otherwise monitor
interfaces could be decrypting frames for other interfaces
that are down at the moment. Also, it should go some way
towards better suspend/resume support, in any case the
routines used here could be used for that as well.
Additionally, this makes the driver interface nicer, keys
for a specific local MAC address are only ever present
while an interface with that MAC address is enabled.
2) Change driver set_key() callback interface to allow only
return values of -ENOSPC, -EOPNOTSUPP and 0, warn on all
other return values. This allows debugging the stack when
a driver notices it's handed a key while it is down.
3) Invert the flag meaning to KEY_FLAG_UPLOADED_TO_HARDWARE.
4) Remove REMOVE_ALL_KEYS command as it isn't used nor do we
want to use it, we'll use DISABLE_KEY for each key. It is
hard to use REMOVE_ALL_KEYS because we can handle multiple
virtual interfaces with different key configuration, so we'd
have to keep track of a lot of state for this and that isn't
worth it.
5) Warn when disabling a key fails, it musn't.
6) Remove IEEE80211_HW_NO_TKIP_WMM_HWACCEL in favour of per-key
IEEE80211_KEY_FLAG_WMM_STA to let driver sort it out itself.
7) Tell driver that a (non-WEP) key is used only for transmission
by using an all-zeroes station MAC address when configuring.
8) Change the set_key() callback to have access to the local MAC
address the key is being added for.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
they aren't really refcounted anyway
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch embeds the struct ieee80211_key_conf into struct ieee80211_key
and thus avoids allocations and having data present twice.
This required some more changes:
1) The removal of the IEEE80211_KEY_DEFAULT_TX_KEY key flag.
This flag isn't used by drivers nor should it be since
we have a set_key_idx() callback. Maybe that callback needs
to be extended to include the key conf, but only a driver that
requires it will tell.
2) The removal of the IEEE80211_KEY_DEFAULT_WEP_ONLY key flag.
This flag is global, so it shouldn't be passed in the key
conf structure. Pass it to the function instead.
Also, this patch removes the AID parameter to the set_key() callback
because it is currently unused and the hardware currently cannot know
about the AID anyway. I suspect this was used with some hardware that
actually selected the AID itself, but that functionality was removed.
Additionally, I've removed the ALG_NULL key algorithm since we have
ALG_NONE.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Michael Wu <flamingice@sourmilk.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
into a new file key.c which doesn't have much code right now but
it makes ieee80211.c easier to read.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Johannes Berg