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Subject[ 41/44] cfg80211: fix interface combinations check for ADHOC(IBSS)
From: Greg KH <>

3.0-stable review patch. If anyone has any objections, please let me know.


From: Liang Li <>

partial of commit 8e8b41f9d8c8e63fc92f899ace8da91a490ac573 upstream.

As part of commit 463454b5dbd8 ("cfg80211: fix interface
combinations check"), this extra check was introduced:

if ((all_iftypes & used_iftypes) != used_iftypes)
goto cont;

However, most wireless NIC drivers did not advertise ADHOC in
wiphy.iface_combinations[i].limits[] and hence we'll get -EBUSY
when we bring up a ADHOC wlan with commands similar to:

# iwconfig wlan0 mode ad-hoc && ifconfig wlan0 up

In commit 8e8b41f9d8c8e ("cfg80211: enforce lack of interface
combinations"), the change below fixes the issue:

if (total == 1)
return 0;

But it also introduces other dependencies for stable. For example,
a full cherry pick of 8e8b41f9d8c8e would introduce additional
regressions unless we also start cherry picking driver specific
fixes like the following:

9b4760e ath5k: add possible wiphy interface combinations
1ae2fc2 mac80211_hwsim: advertise interface combinations
20c8e8d ath9k: add possible wiphy interface combinations

And the purpose of the 'if (total == 1)' is to cover the specific
use case (IBSS, adhoc) that was mentioned above. So we just pick
the specific part out from 8e8b41f9d8c8e here.

Doing so gives stable kernels a way to fix the change introduced
by 463454b5dbd8, without having to make cherry picks specific to
various NIC drivers.

Signed-off-by: Liang Li <>
Signed-off-by: Paul Gortmaker <>
Signed-off-by: Greg Kroah-Hartman <>

net/wireless/util.c | 3 +++
1 file changed, 3 insertions(+)

--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -975,6 +975,9 @@ int cfg80211_can_change_interface(struct

+ if (total == 1)
+ return 0;
for (i = 0; i < rdev->wiphy.n_iface_combinations; i++) {
const struct ieee80211_iface_combination *c;
struct ieee80211_iface_limit *limits;

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