[PATCH 4.1 55/78] mac80211: fix invalid read in minstrel_sort_best_tp_rates()

Greg Kroah-Hartman
2015-09-11T22:51:03Z

From: Adrien Schildknecht <adrien+dev@schischi.me>

commit f5eeb5fa191fd7b634cbc4883ac58f3b2184dbc5 upstream.

At the last iteration of the loop, j may equal zero and thus
tp_list[j - 1] causes an invalid read.
Change the logic of the loop so that j - 1 is always >= 0.

Signed-off-by: Adrien Schildknecht <adrien+dev@schischi.me>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/mac80211/rc80211_minstrel.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -92,14 +92,15 @@ int minstrel_get_tp_avg(struct minstrel_
static inline void
minstrel_sort_best_tp_rates(struct minstrel_sta_info *mi, int i, u8 *tp_list)
{
- int j = MAX_THR_RATES;
- struct minstrel_rate_stats *tmp_mrs = &mi->r[j - 1].stats;
+ int j;
+ struct minstrel_rate_stats *tmp_mrs;
struct minstrel_rate_stats *cur_mrs = &mi->r[i].stats;

- while (j > 0 && (minstrel_get_tp_avg(&mi->r[i], cur_mrs->prob_ewma) >
- minstrel_get_tp_avg(&mi->r[tp_list[j - 1]], tmp_mrs->prob_ewma))) {
- j--;
+ for (j = MAX_THR_RATES; j > 0; --j) {
tmp_mrs = &mi->r[tp_list[j - 1]].stats;
+ if (minstrel_get_tp_avg(&mi->r[i], cur_mrs->prob_ewma) <=
+ minstrel_get_tp_avg(&mi->r[tp_list[j - 1]], tmp_mrs->prob_ewma))
+ break;
}

if (j < MAX_THR_RATES - 1)