A bug just got reported as a result of this for mac80211 drivers.
https://bugzilla.redhat.com/show_bug.cgi?id=459399
The basic problem is that since taking the device down clears the keys
from the driver on many mac80211-based cards, and since the mode gets
set _after_ the keys have been set in the driver, the keys get cleared
on a mode switch and the resulting association is wrong. The report is
about ad-hoc mode specifically, but this could happen when switching
from adhoc back to managed mode.
If IWEVGENIE or custom event wpa_ie/rsn_ie is received in scan with empty
buffer, the previous version ended up calling realloc(NULL, 0) which seems
to return a non-NULL value in some cases. When this return value is passed
again into realloc with realloc(ptr, 0), the returned value could be NULL.
If the ptr is then freed (os_free(data.ie) in SIOCGIWAP handling), glibc
may crash due to invalid pointer being freed (or double-freed?). The
non-NULL realloc(NULL, 0) return value from glibc looks a bit odd behavior,
but anyway, better avoid this case completely and just skip the IE events
that have an empty buffer.
This issue should not show up with drivers that produce proper scan results
since the IEs will always include the two-octet header. However, it seems
to be possible to see this when using 64-bit kernel and 32-bit userspace
with incorrect compat-ioctl processing.
These functions are based on the hostapd implementation and complete
the userspace MLME code in wpa_supplicant (though, mac80211 will still need
couple of pending patches to be integrated in order to get userspace client
MLME working again).
This adds some parts needed to use usermode MLME with the current mac80211
(plus a patch to add a new cfg80211 command; not yet submitted to
wireless-testing). This version creates a monitor interface for management
frames and is able to send Probe Request frames during scan. However, it
looks like management frame reception is not yet working properly. In
addition, mlme_{add,remove}_sta() handlers are still missing.
Network device ifindex will change when the interface is re-inserted.
driver_nl80211.c will need to accept netlink events from "unknown" (based
on ifindex) interfaces when a previously used card was removed earlier. If
the previously removed interface is added back, the driver_wext data need
to be updated to match with the new ifindex value. In addition, the initial
setup tasks for the card (set interface up, update ifindex, set mode, etc.)
from wpa_driver_nl80211_init() need to be run again.
This is the changes from commit 3fbda8f943
(driver_wext.c) ported for driver_nl80211.c.
When scan results got moved from wpa_scan_result -> wpa_scan_res, the
'maxrate' member was dropped from wpa_scan_res. The D-Bus interface
used 'maxrate', which was replaced with wpa_scan_get_max_rate().
Unfortunately, wpa_scan_get_max_rate() returns 802.11 rate values
directly from the IE, where 'maxrate' was the rate in bits/second. The
supplicant internally fakes an IE for wpa_scan_res from the value of
wpa_scan_result->maxrate, but interprets ->maxrate as an 802.11 rate
index.
As a side-effect, this fixes a soft-break of the D-Bus control API since
the wpa_scan_res change was introduced.
driver_nl80211.c is based on driver_wext.c and it is still using Linux
wireless extensions for many functions. Over time, the new driver interface
code should be modified to use nl80211/cfg80211 for everything.
