[3.11.y.z extended stable] Patch "ath9k: protect tid->sched check" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ath9k: protect tid->sched check

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2c1b1bd8d7e8859aebfa443c698d11e2739743fa Mon Sep 17 00:00:00 2001
From: Stanislaw Gruszka <sgruszka at redhat.com>
Date: Wed, 19 Feb 2014 13:15:17 +0100
Subject: ath9k: protect tid->sched check

commit 21f8aaee0c62708654988ce092838aa7df4d25d8 upstream.

We check tid->sched without a lock taken on ath_tx_aggr_sleep(). That
is race condition which can result of doing list_del(&tid->list) twice
(second time with poisoned list node) and cause crash like shown below:

[424271.637220] BUG: unable to handle kernel paging request at 00100104
[424271.637328] IP: [<f90fc072>] ath_tx_aggr_sleep+0x62/0xe0 [ath9k]
...
[424271.639953] Call Trace:
[424271.639998]  [<f90f6900>] ? ath9k_get_survey+0x110/0x110 [ath9k]
[424271.640083]  [<f90f6942>] ath9k_sta_notify+0x42/0x50 [ath9k]
[424271.640177]  [<f809cfef>] sta_ps_start+0x8f/0x1c0 [mac80211]
[424271.640258]  [<c10f730e>] ? free_compound_page+0x2e/0x40
[424271.640346]  [<f809e915>] ieee80211_rx_handlers+0x9d5/0x2340 [mac80211]
[424271.640437]  [<c112f048>] ? kmem_cache_free+0x1d8/0x1f0
[424271.640510]  [<c1345a84>] ? kfree_skbmem+0x34/0x90
[424271.640578]  [<c10fc23c>] ? put_page+0x2c/0x40
[424271.640640]  [<c1345a84>] ? kfree_skbmem+0x34/0x90
[424271.640706]  [<c1345a84>] ? kfree_skbmem+0x34/0x90
[424271.640787]  [<f809dde3>] ? ieee80211_rx_handlers_result+0x73/0x1d0 [mac80211]
[424271.640897]  [<f80a07a0>] ieee80211_prepare_and_rx_handle+0x520/0xad0 [mac80211]
[424271.641009]  [<f809e22d>] ? ieee80211_rx_handlers+0x2ed/0x2340 [mac80211]
[424271.641104]  [<c13846ce>] ? ip_output+0x7e/0xd0
[424271.641182]  [<f80a1057>] ieee80211_rx+0x307/0x7c0 [mac80211]
[424271.641266]  [<f90fa6ee>] ath_rx_tasklet+0x88e/0xf70 [ath9k]
[424271.641358]  [<f80a0f2c>] ? ieee80211_rx+0x1dc/0x7c0 [mac80211]
[424271.641445]  [<f90f82db>] ath9k_tasklet+0xcb/0x130 [ath9k]

Bug report:
https://bugzilla.kernel.org/show_bug.cgi?id=70551

Reported-and-tested-by: Max Sydorenko <maxim.stargazer at gmail.com>
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/wireless/ath/ath9k/xmit.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index ab64683..f0aaeb2 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -1318,14 +1318,16 @@ void ath_tx_aggr_sleep(struct ieee80211_sta *sta, struct ath_softc *sc,
 	for (tidno = 0, tid = &an->tid[tidno];
 	     tidno < IEEE80211_NUM_TIDS; tidno++, tid++) {

-		if (!tid->sched)
-			continue;
-
 		ac = tid->ac;
 		txq = ac->txq;

 		ath_txq_lock(sc, txq);

+		if (!tid->sched) {
+			ath_txq_unlock(sc, txq);
+			continue;
+		}
+
 		buffered = !skb_queue_empty(&tid->buf_q);

 		tid->sched = false;
--
1.9.0