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>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index ac7ef5414bde..e6512e2ffd20 100644
--- 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;