[PATCH 4.9 027/134] mac80211: fix potential overflow when multiplying to u32 integers

[Greg Kroah-Hartman]

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

[ Upstream commit 6194f7e6473be78acdc5d03edd116944bdbb2c4e ]

The multiplication of the u32 variables tx_time and estimated_retx is
performed using a 32 bit multiplication and the result is stored in
a u64 result. This has a potential u32 overflow issue, so avoid this
by casting tx_time to a u64 to force a 64 bit multiply.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 050ac52cbe1f ("mac80211: code for on-demand Hybrid Wireless Mesh Protocol")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210205175352.208841-1-colin.king@xxxxxxxxxxxxx
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/mac80211/mesh_hwmp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mac80211/mesh_hwmp.c b/net/mac80211/mesh_hwmp.c
index 2fbd100b9e73d..a8b837d0498a4 100644
--- a/net/mac80211/mesh_hwmp.c
+++ b/net/mac80211/mesh_hwmp.c
@@ -355,7 +355,7 @@ static u32 airtime_link_metric_get(struct ieee80211_local *local,
 	 */
 	tx_time = (device_constant + 10 * test_frame_len / rate);
 	estimated_retx = ((1 << (2 * ARITH_SHIFT)) / (s_unit - err));
-	result = (tx_time * estimated_retx) >> (2 * ARITH_SHIFT);
+	result = ((u64)tx_time * estimated_retx) >> (2 * ARITH_SHIFT);
 	return (u32)result;
 }
 
-- 
2.27.0