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From: Felix Fietkau <nbd@openwrt.org>
Date: Tue, 18 Nov 2014 21:43:25 +0100
Subject: [PATCH] mac80211: minstrel_ht: fix a crash in rate sorting
The commit 5935839ad73583781b8bbe8d91412f6826e218a4
"mac80211: improve minstrel_ht rate sorting by throughput & probability"
introduced a crash on rate sorting that occurs when the rate added to
the sorting array is faster than all the previous rates. Due to an
off-by-one error, it reads the rate index from tp_list[-1], which
contains uninitialized stack garbage, and then uses the resulting index
for accessing the group rate stats, leading to a crash if the garbage
value is big enough.
Cc: Thomas Huehn <thomas@net.t-labs.tu-berlin.de>
Reported-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
---
--- a/net/mac80211/rc80211_minstrel_ht.c
+++ b/net/mac80211/rc80211_minstrel_ht.c
@@ -394,19 +394,16 @@ minstrel_ht_sort_best_tp_rates(struct mi
cur_thr = mi->groups[cur_group].rates[cur_idx].cur_tp;
cur_prob = mi->groups[cur_group].rates[cur_idx].probability;
- tmp_group = tp_list[j - 1] / MCS_GROUP_RATES;
- tmp_idx = tp_list[j - 1] % MCS_GROUP_RATES;
- tmp_thr = mi->groups[tmp_group].rates[tmp_idx].cur_tp;
- tmp_prob = mi->groups[tmp_group].rates[tmp_idx].probability;
-
- while (j > 0 && (cur_thr > tmp_thr ||
- (cur_thr == tmp_thr && cur_prob > tmp_prob))) {
- j--;
+ do {
tmp_group = tp_list[j - 1] / MCS_GROUP_RATES;
tmp_idx = tp_list[j - 1] % MCS_GROUP_RATES;
tmp_thr = mi->groups[tmp_group].rates[tmp_idx].cur_tp;
tmp_prob = mi->groups[tmp_group].rates[tmp_idx].probability;
- }
+ if (cur_thr < tmp_thr ||
+ (cur_thr == tmp_thr && cur_prob <= tmp_prob))
+ break;
+ j--;
+ } while (j > 0);
if (j < MAX_THR_RATES - 1) {
memmove(&tp_list[j + 1], &tp_list[j], (sizeof(*tp_list) *
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