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@xxxxxxxxxxxxxxx
Signed-off-by: Ilia Gavrilov <Ilia.Gavrilov@xxxxxxxxxxx>
---
v2:
- Remove 64-bit arithmetic according to https://lore.kernel.org/all/a6bd38c58f2f7685eac53844f2336432503c328e.camel@xxxxxxxxxxxxxxxx/
- Replace multiplication by 10/9 with a function that compares metrics by adding 10% without integer overflow
v3:
- Fix a typo (persent->percent)
net/mac80211/mesh_hwmp.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 4e9546e998b6..79aa29d61e6b 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -367,6 +367,26 @@ u32 airtime_link_metric_get(struct ieee80211_local *local,
return (u32)result;
}
+static inline bool is_metric_better(u32 x, u32 y, u32 percent)
+{
+ u32 a, e;
+
+ if (x >= y)
+ return false;
+
+ a = mult_frac(x, percent, 100);
+
+ if (check_add_overflow(x, a, &e)) {
+ if (x > y - a)
+ return false;
+ } else {
+ if (e > y)
+ return false;
+ }
+
+ return true;
+}
+
/**
* hwmp_route_info_get - Update routing info to originator and transmitter
*
@@ -458,8 +478,8 @@ 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, 10) :
+ new_metric >= mpath->metric))) {
process = false;
fresh_info = false;
}
@@ -533,8 +553,8 @@ 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, 10) :
+ last_hop_metric > mpath->metric))))
fresh_info = false;
} else {
mpath = mesh_path_add(sdata, ta);
--
2.39.5
