mac80211: fix divide by zero when NOA update

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@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 01fe82e9d1b0ec66a7a20dca403d611c9b0f3ed1..c68e6cf4367ef6de09646ae08d85bcad59ed056a 100644 (file)
--- 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) {