From: Johannes Berg Date: Wed, 23 Dec 2009 12:12:05 +0000 (+0100) Subject: cfg80211: fix race between deauth and assoc response X-Git-Tag: MMI-PSA29.97-13-9~24911^2~1^2~59 X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3bdb2d48c5f58c781a4099c99044384a23620884;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git cfg80211: fix race between deauth and assoc response Joseph Nahmias reported, in http://bugs.debian.org/562016, that he was getting the following warning (with some log around the issue): ath0: direct probe to AP 00:11:95:77:e0:b0 (try 1) ath0: direct probe responded ath0: authenticate with AP 00:11:95:77:e0:b0 (try 1) ath0: authenticated ath0: associate with AP 00:11:95:77:e0:b0 (try 1) ath0: deauthenticating from 00:11:95:77:e0:b0 by local choice (reason=3) ath0: direct probe to AP 00:11:95:77:e0:b0 (try 1) ath0: RX AssocResp from 00:11:95:77:e0:b0 (capab=0x421 status=0 aid=2) ath0: associated ------------[ cut here ]------------ WARNING: at net/wireless/mlme.c:97 cfg80211_send_rx_assoc+0x14d/0x152 [cfg80211]() Hardware name: 7658CTO ... Pid: 761, comm: phy0 Not tainted 2.6.32-trunk-686 #1 Call Trace: [] ? warn_slowpath_common+0x5e/0x8a [] ? warn_slowpath_null+0xa/0xc [] ? cfg80211_send_rx_assoc+0x14d/0x152 ... ath0: link becomes ready ath0: deauthenticating from 00:11:95:77:e0:b0 by local choice (reason=3) ath0: no IPv6 routers present ath0: link is not ready ath0: direct probe to AP 00:11:95:77:e0:b0 (try 1) ath0: direct probe responded ath0: authenticate with AP 00:11:95:77:e0:b0 (try 1) ath0: authenticated ath0: associate with AP 00:11:95:77:e0:b0 (try 1) ath0: RX ReassocResp from 00:11:95:77:e0:b0 (capab=0x421 status=0 aid=2) ath0: associated It is not clear to me how the first "direct probe" here happens, but this seems to be a race condition, if the user requests to deauth after requesting assoc, but before the assoc response is received. In that case, it may happen that mac80211 tries to report the assoc success to cfg80211, but gets blocked on the wdev lock that is held because the user is requesting the deauth. The result is that we run into a warning. This is mostly harmless, but maybe cause an unexpected event to be sent to userspace; we'd send an assoc success event although userspace was no longer expecting that. To fix this, remove the warning and check whether the race happened and in that case abort processing. Reported-by: Joseph Nahmias Cc: stable@kernel.org Cc: 562016-quiet@bugs.debian.org Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- diff --git a/net/wireless/mlme.c b/net/wireless/mlme.c index 1001db4912f7..82e6002c8d67 100644 --- a/net/wireless/mlme.c +++ b/net/wireless/mlme.c @@ -93,7 +93,18 @@ void cfg80211_send_rx_assoc(struct net_device *dev, const u8 *buf, size_t len) } } - WARN_ON(!bss); + /* + * We might be coming here because the driver reported + * a successful association at the same time as the + * user requested a deauth. In that case, we will have + * removed the BSS from the auth_bsses list due to the + * deauth request when the assoc response makes it. If + * the two code paths acquire the lock the other way + * around, that's just the standard situation of a + * deauth being requested while connected. + */ + if (!bss) + goto out; } else if (wdev->conn) { cfg80211_sme_failed_assoc(wdev); /*