2018-03-26 13:21:09

by Grumbach, Emmanuel

Subject: [PATCH] mac80211: don't WARN on bad WMM parameters from buggy APs

Apparently, some APs are buggy enough to send a zeroed
WMM IE. Don't WARN on this since this is not caused by a bug
on the client's system.

This aligns the condition of the WARNING in drv_conf_tx
with the validity check in ieee80211_sta_wmm_params.
We will now pick the default values whenever we get
a zeroed WMM IE.

This has been reported here:
https://bugzilla.kernel.org/show_bug.cgi?id=199161

Signed-off-by: Emmanuel Grumbach <[email protected]>
---
net/mac80211/mlme.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 39b660b9a908..a6b628964b84 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1785,7 +1785,8 @@ static bool ieee80211_sta_wmm_params(struct ieee80211_local *local,
params[ac].acm = acm;
params[ac].uapsd = uapsd;

- if (params[ac].cw_min > params[ac].cw_max) {
+ if (params->cw_min == 0 ||
+ params[ac].cw_min > params[ac].cw_max) {
sdata_info(sdata,
"AP has invalid WMM params (CWmin/max=%d/%d for ACI %d), using defaults\n",
params[ac].cw_min, params[ac].cw_max, aci);
--
2.14.3

2018-04-17 12:11:03

by Christian Lamparter

Subject: Re: [PATCH] mac80211: don't WARN on bad WMM parameters from buggy APs

Hello,

On Monday, 26. March 2018 15:21:04 CEST Emmanuel Grumbach wrote:
> Apparently, some APs are buggy enough to send a zeroed
> WMM IE. Don't WARN on this since this is not caused by a bug
> on the client's system.
>
> This aligns the condition of the WARNING in drv_conf_tx
> with the validity check in ieee80211_sta_wmm_params.
> We will now pick the default values whenever we get
> a zeroed WMM IE.
>
> This has been reported here:
> https://bugzilla.kernel.org/show_bug.cgi?id=199161
>
> Signed-off-by: Emmanuel Grumbach <[email protected]>
> ---
> net/mac80211/mlme.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index 39b660b9a908..a6b628964b84 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -1785,7 +1785,8 @@ static bool ieee80211_sta_wmm_params(struct ieee80211_local *local,
> params[ac].acm = acm;
> params[ac].uapsd = uapsd;
>
> - if (params[ac].cw_min > params[ac].cw_max) {
> + if (params->cw_min == 0 ||
I'm getting:
[ 164.503843] wlan0: AP has invalid WMM params (CWmin/max=15/1023 for ACI 0), using defaults

The AP is running a recent OpenWrt and is using hostapd 2.7.

iw says the AP has the following WMM IE:
Extended capabilities: Extended Channel Switching, SSID List, 6
WMM: * Parameter version 1
* u-APSD
* BE: CW 15-1023, AIFSN 3
* BK: CW 15-1023, AIFSN 7
* VI: CW 7-15, AIFSN 2, TXOP 3008 usec
* VO: CW 3-7, AIFSN 2, TXOP 1504 usec

which looks reasonable.

What seems to be happening is that the code now expects to start
with ac = 0.

802.11-2012's Figure 8-192 EDCA Parameter Set element lists the AC_BE as the
first element in the IE and because of this ac variable gets set to
IEEE80211_AC_BE [1] in the first round. This would be fine, if
IEEE80211_AC_BE was 0, but it is 2 [2].

Should this be params[ac].cw_min? or params[aci].cw_min?
Or should the params->cw_min check be placed after the loop?
Can you please sent a fix? Thanks.

Regards,
Christian

[1] <https://elixir.bootlin.com/linux/v4.17-rc1/source/net/mac80211/mlme.c#L1768>
[2] <https://elixir.bootlin.com/linux/v4.17-rc1/source/include/net/mac80211.h#L148>

2018-04-17 14:51:11

by Johannes Berg

Subject: Re: [PATCH] mac80211: don't WARN on bad WMM parameters from buggy APs

On Tue, 2018-04-17 at 14:11 +0200, Christian Lamparter wrote:
>
> > - if (params[ac].cw_min > params[ac].cw_max) {
> > + if (params->cw_min == 0 ||

Yeah. We already have a fix pending

https://patchwork.kernel.org/patch/10320823/

I just haven't been keeping up during the merge window.

johannes