mac80211/minstrel: fix NULL pointer dereference issue

When priv_sta == NULL, mi->prev_sample is dereferenced too early. Move
the assignment further down, after the rate_control_send_low call.

Reported-by: Krzysztof Mazur <krzysiek@podlesie.net>
Cc: stable@vger.kernel.org # 3.10
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index ac7ef54..e6512e2 100644 (file)
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -290,7 +290,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
        struct minstrel_rate *msr, *mr;
        unsigned int ndx;
        bool mrr_capable;
-       bool prev_sample = mi->prev_sample;
+       bool prev_sample;
        int delta;
        int sampling_ratio;
 
@@ -314,6 +314,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
                        (mi->sample_count + mi->sample_deferred / 2);
 
        /* delta < 0: no sampling required */
+       prev_sample = mi->prev_sample;
        mi->prev_sample = false;
        if (delta < 0 || (!mrr_capable && prev_sample))
                return;