We are seeing panics coming out of wiphy_update_regulatory() from LBM on
both Jaunty and Intrepid. These two carry the same basic code for the
wireless stack. Sample stack trace as here:
[ 398.693189] BUG: unable to handle kernel NULL pointer dereference at
00000004
[ 398.693206] IP: [<f8e1feb4>]
:lbm_cw_cfg80211:wiphy_update_regulatory+0x1d4/0x420
[ 398.693232] *pde = 00000000
[ 398.693242] Oops: 0000 [#1] SMP
[...]
[ 398.693479]
[ 398.693487] Pid: 6314, comm: modprobe Not tainted (2.6.27-14-generic #1)
[ 398.693496] EIP: 0060:[<f8e1feb4>] EFLAGS: 00010246 CPU: 1
[ 398.693514] EIP is at wiphy_update_regulatory+0x1d4/0x420
[lbm_cw_cfg80211]
[ 398.693523] EAX: 00000000 EBX: 00000410 ECX: f52e0060 EDX: 00000001
[ 398.693532] ESI: f52e0000 EDI: f52e0060 EBP: f520fcb0 ESP: f520fc78
[ 398.693541] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[ 398.693550] Process modprobe (pid: 6314, ti=f520e000 task=f5250000
task.ti=f520e000)
[ 398.693558] Stack: c018a2ee c0495500 f52e0060 f6603000 f520fcc8 c01050f8
00004e17 013ef000
[ 398.693581] 00000099 f8e1eece f52e0060 00000410 f52e0000 f52e0060
f520fccc f8e1e52e
[ 398.693603] 00000002 00000002 fffffff4 00000000 f52e01e0 f520fd00
f8f472f0 00006957
The key thing to note is that we are panicing with a data reference to
address 0x4. This is classically a structure offset relative to a NULL
pointer. Looking at this function when we are called we may look at the
band, and then we will handle beacons, and finally we will give the PHY
a chance to see the information via the reg_notifier. None of the
referenced information is at offset 0x4 in the structure:
void wiphy_update_regulatory(struct wiphy *wiphy,
enum nl80211_reg_initiator initiator)
{
enum ieee80211_band band;
if (ignore_reg_update(wiphy, initiator))
goto out;
for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
if (wiphy->bands[band])
handle_band(wiphy, band);
}
out:
reg_process_beacons(wiphy);
if (wiphy->reg_notifier)
wiphy->reg_notifier(wiphy, last_request);
}
Looking at the reg_process_beacons() we can see it cals:
reg_is_world_romaing():
/* Reap the advantages of previously found beacons */
static void reg_process_beacons(struct wiphy *wiphy)
{
if (!reg_is_world_roaming(wiphy))
return;
wiphy_update_beacon_reg(wiphy);
}
and that references last_request->initiator:
static bool reg_is_world_roaming(struct wiphy *wiphy)
{
if (is_world_regdom(cfg80211_regdomain->alpha2) ||
(wiphy->regd && is_world_regdom(wiphy->regd->alpha2)))
return true;
if (last_request->initiator != NL80211_REGDOM_SET_BY_COUNTRY_IE &&
wiphy->custom_regulatory)
return true;
return false;
}
and _that_ is at offset 4, and as these two are static they are likely
inlined into wiphy_update_regulatory():
struct regulatory_request {
int wiphy_idx;
enum nl80211_reg_initiator initiator;
[...]
};
Note also that the definition of ignore_reg_updates() does the
following:
static bool ignore_reg_update(struct wiphy *wiphy,
enum nl80211_reg_initiator initiator)
{
if (!last_request)
return true;
[...]
}
So, it is entirly possible to call wiphy_update_regulatory() with
last_request == NULL, and for that to trigger us to call down to
reg_process_beacons() to reg_process_beacons() to reg_is_world_roaming()
which then reference last_request assuming it is not NULL leading to a
panic referencing 0x4.
As a side note we will also call any notifiers with las_request as NULL
and cirtainly the ath9k notifier is not expecting that to be so which
would likely also blammo in the same manner:
int ath9k_reg_notifier(struct wiphy *wiphy, struct regulatory_request
*request)
{
[...]
switch (request->initiator) {
[...]
}
It seems likely we should not perform any of this processing is
last_request is null. Will patch this up for testing.
--
ieee80211_regdom=EU now causes oops after latest update
https://bugs.launchpad.net/bugs/337929
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