linux-kernel - [PATCH 4.2 066/124] mac80211: fix divide by zero when NOA update

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Message-Id: <20151207144922.936734291@linuxfoundation.org>
Date:	Mon,  7 Dec 2015 09:55:56 -0500
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Janusz Dziedzic <janusz.dziedzic@...to.com>,
	Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH 4.2 066/124] mac80211: fix divide by zero when NOA update

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

------------------

From: "Janusz.Dziedzic@...to.com" <Janusz.Dziedzic@...to.com>

commit 519ee6918b91abdc4bc9720deae17599a109eb40 upstream.

In case of one shot NOA the interval can be 0, catch that
instead of potentially (depending on the driver) crashing
like this:

divide error: 0000 [#1] SMP
[...]
Call Trace:
<IRQ>
[<ffffffffc08e891c>] ieee80211_extend_absent_time+0x6c/0xb0 [mac80211]
[<ffffffffc08e8a17>] ieee80211_update_p2p_noa+0xb7/0xe0 [mac80211]
[<ffffffffc069cc30>] ath9k_p2p_ps_timer+0x170/0x190 [ath9k]
[<ffffffffc070adf8>] ath_gen_timer_isr+0xc8/0xf0 [ath9k_hw]
[<ffffffffc0691156>] ath9k_tasklet+0x296/0x2f0 [ath9k]
[<ffffffff8107ad65>] tasklet_action+0xe5/0xf0
[...]

Signed-off-by: Janusz Dziedzic <janusz.dziedzic@...to.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/mac80211/util.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -2984,6 +2984,13 @@ ieee80211_extend_noa_desc(struct ieee802
 	if (end > 0)
 		return false;
 
+	/* One shot NOA  */
+	if (data->count[i] == 1)
+		return false;
+
+	if (data->desc[i].interval == 0)
+		return false;
+
 	/* End time is in the past, check for repetitions */
 	skip = DIV_ROUND_UP(-end, data->desc[i].interval);
 	if (data->count[i] < 255) {


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