wifi: mac80211: fix integer overflow in hwmp_route_info_get()

Since the new_metric and last_hop_metric variables can reach
the MAX_METRIC(0xffffffff) value, an integer overflow may occur
when multiplying them by 10/9. It can lead to incorrect behavior.

Found by InfoTeCS on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: a8d418d9ac25 ("mac80211: mesh: only switch path when new metric is at least 10% better")
Cc: stable@vger.kernel.org
Signed-off-by: Ilia Gavrilov <Ilia.Gavrilov@infotecs.ru>
Link: https://patch.msgid.link/20250212082124.4078236-1-Ilia.Gavrilov@infotecs.ru
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 4e9546e998b6d119cdfdf07026d7f73391d6d8e8..c94a9c7ca960efb63d6a221acae054db2323616e 100644 (file)
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -367,6 +367,12 @@ u32 airtime_link_metric_get(struct ieee80211_local *local,
        return (u32)result;
 }
 
+/* Check that the first metric is at least 10% better than the second one */
+static bool is_metric_better(u32 x, u32 y)
+{
+       return (x < y) && (x < (y - x / 10));
+}
+
 /**
  * hwmp_route_info_get - Update routing info to originator and transmitter
  *
@@ -458,8 +464,8 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
                                    (mpath->sn == orig_sn &&
                                     (rcu_access_pointer(mpath->next_hop) !=
                                                      sta ?
-                                             mult_frac(new_metric, 10, 9) :
-                                             new_metric) >= mpath->metric)) {
+                                             !is_metric_better(new_metric, mpath->metric) :
+                                             new_metric >= mpath->metric))) {
                                        process = false;
                                        fresh_info = false;
                                }
@@ -533,8 +539,8 @@ static u32 hwmp_route_info_get(struct ieee80211_sub_if_data *sdata,
                        if ((mpath->flags & MESH_PATH_FIXED) ||
                            ((mpath->flags & MESH_PATH_ACTIVE) &&
                             ((rcu_access_pointer(mpath->next_hop) != sta ?
-                                      mult_frac(last_hop_metric, 10, 9) :
-                                      last_hop_metric) > mpath->metric)))
+                                     !is_metric_better(last_hop_metric, mpath->metric) :
+                                      last_hop_metric > mpath->metric))))
                                fresh_info = false;
                } else {
                        mpath = mesh_path_add(sdata, ta);