[PATCH] wifi: mac80211: fix interger overflow in hwmp_route_info_get()

[PATCH] wifi: mac80211: fix interger overflow in hwmp_route_info_get()

[Gavrilov Ilia]

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>
---
 net/mac80211/mesh_hwmp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 4e9546e998b6..7d367ff1efc2 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -458,7 +458,7 @@ 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) :
+					      mult_frac((u64)new_metric, 10, 9) :
 					      new_metric) >= mpath->metric)) {
 					process = false;
 					fresh_info = false;
@@ -533,7 +533,7 @@ 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) :
+				       mult_frac((u64)last_hop_metric, 10, 9) :
 				       last_hop_metric) > mpath->metric)))
 				fresh_info = false;
 		} else {
-- 
2.39.5

Re: [PATCH] wifi: mac80211: fix interger overflow in hwmp_route_info_get()

[Johannes Berg]

On Thu, 2024-12-26 at 07:47 +0000, Gavrilov Ilia wrote:
> 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.
> 
> -					      mult_frac(new_metric, 10, 9) :
> +					      mult_frac((u64)new_metric, 10, 9) :
> 

As you would expect, this doesn't build on 32-bit.

johannnes