linux-kernel - [PATCH 3.16.y-ckt 054/126] mac80211: fix divide by zero when NOA update

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Message-Id: <1449653896-5236-55-git-send-email-luis.henriques@canonical.com>
Date:	Wed,  9 Dec 2015 09:37:04 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Janusz Dziedzic <janusz.dziedzic@...to.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 054/126] mac80211: fix divide by zero when NOA update

3.16.7-ckt21 -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: Luis Henriques <luis.henriques@...onical.com>
---
 net/mac80211/util.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 01fe82e9d1b0..c68e6cf4367e 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -2664,6 +2664,13 @@ ieee80211_extend_noa_desc(struct ieee80211_noa_data *data, u32 tsf, int i)
 	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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