iwlwifi: mvm: fix possible out-of-bounds read when accessing lq_info

lq_info is an arary of size 2, active_tbl index is u8.
When accessing lq_info[1 - active_tbl], theoretically it's possible
that the access will be made to a negative index value.

Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
index 3fa50b1955bbde196258d188f3f241ec47f5750a..d3f04acfbacb9fa360388110423391f6032ea2ca 100644 (file)
--- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
@@ -1352,6 +1352,18 @@ static void rs_set_expected_tpt_table(struct iwl_lq_sta *lq_sta,
        tbl->expected_tpt = rs_get_expected_tpt_table(lq_sta, column, rate->bw);
 }
 
+/* rs uses two tables, one is active and the second is for searching better
+ * configuration. This function, according to the index of the currently
+ * active table returns the search table, which is located at the
+ * index complementary to 1 according to the active table (active = 1,
+ * search = 0 or active = 0, search = 1).
+ * Since lq_info is an arary of size 2, make sure index cannot be out of bounds.
+ */
+static inline u8 rs_search_tbl(u8 active_tbl)
+{
+       return (active_tbl ^ 1) & 1;
+}
+
 static s32 rs_get_best_rate(struct iwl_mvm *mvm,
                            struct iwl_lq_sta *lq_sta,
                            struct iwl_scale_tbl_info *tbl,     /* "search" */
@@ -1699,9 +1711,9 @@ static int rs_switch_to_column(struct iwl_mvm *mvm,
                               struct ieee80211_sta *sta,
                               enum rs_column col_id)
 {
-       struct iwl_scale_tbl_info *tbl = &(lq_sta->lq_info[lq_sta->active_tbl]);
+       struct iwl_scale_tbl_info *tbl = &lq_sta->lq_info[lq_sta->active_tbl];
        struct iwl_scale_tbl_info *search_tbl =
-                               &(lq_sta->lq_info[(1 - lq_sta->active_tbl)]);
+               &lq_sta->lq_info[rs_search_tbl(lq_sta->active_tbl)];
        struct rs_rate *rate = &search_tbl->rate;
        const struct rs_tx_column *column = &rs_tx_columns[col_id];
        const struct rs_tx_column *curr_column = &rs_tx_columns[tbl->column];
@@ -2109,7 +2121,7 @@ static void rs_rate_scale_perform(struct iwl_mvm *mvm,
        if (!lq_sta->search_better_tbl)
                active_tbl = lq_sta->active_tbl;
        else
-               active_tbl = 1 - lq_sta->active_tbl;
+               active_tbl = rs_search_tbl(lq_sta->active_tbl);
 
        tbl = &(lq_sta->lq_info[active_tbl]);
        rate = &tbl->rate;
@@ -2333,7 +2345,7 @@ lq_update:
                /* If new "search" mode was selected, set up in uCode table */
                if (lq_sta->search_better_tbl) {
                        /* Access the "search" table, clear its history. */
-                       tbl = &(lq_sta->lq_info[(1 - lq_sta->active_tbl)]);
+                       tbl = &lq_sta->lq_info[rs_search_tbl(lq_sta->active_tbl)];
                        rs_rate_scale_clear_tbl_windows(mvm, tbl);
 
                        /* Use new "search" start rate */
@@ -2676,7 +2688,7 @@ static void rs_initialize_lq(struct iwl_mvm *mvm,
        if (!lq_sta->search_better_tbl)
                active_tbl = lq_sta->active_tbl;
        else
-               active_tbl = 1 - lq_sta->active_tbl;
+               active_tbl = rs_search_tbl(lq_sta->active_tbl);
 
        tbl = &(lq_sta->lq_info[active_tbl]);
        rate = &tbl->rate;
@@ -3172,9 +3184,9 @@ static void __iwl_mvm_rs_tx_status(struct iwl_mvm *mvm,
 
        if (!lq_sta->search_better_tbl) {
                curr_tbl = &lq_sta->lq_info[lq_sta->active_tbl];
-               other_tbl = &lq_sta->lq_info[1 - lq_sta->active_tbl];
+               other_tbl = &lq_sta->lq_info[rs_search_tbl(lq_sta->active_tbl)];
        } else {
-               curr_tbl = &lq_sta->lq_info[1 - lq_sta->active_tbl];
+               curr_tbl = &lq_sta->lq_info[rs_search_tbl(lq_sta->active_tbl)];
                other_tbl = &lq_sta->lq_info[lq_sta->active_tbl];
        }
 
@@ -3183,7 +3195,7 @@ static void __iwl_mvm_rs_tx_status(struct iwl_mvm *mvm,
                               "Neither active nor search matches tx rate\n");
                tmp_tbl = &lq_sta->lq_info[lq_sta->active_tbl];
                rs_dump_rate(mvm, &tmp_tbl->rate, "ACTIVE");
-               tmp_tbl = &lq_sta->lq_info[1 - lq_sta->active_tbl];
+               tmp_tbl = &lq_sta->lq_info[rs_search_tbl(lq_sta->active_tbl)];
                rs_dump_rate(mvm, &tmp_tbl->rate, "SEARCH");
                rs_dump_rate(mvm, &lq_rate, "ACTUAL");