[PATCH RFC net] openvswitch: fix possible integer overflow in ovs_meter_execute

In 'ovs_meter_execute()', add warn on multiplication of 'delta_ms' and
'band->rate'. The value of 'delta_ms' depends on 'meter->max_delta_t'
which in turn calculates based on user defined burst_size it can leads
to integer overflow.
Compile tested only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Dmitry Kandybka <redacted>
---
Not tested. I am sending this as an RFC because I am not able to 
reproduce the issue in-house and I am not found any proof in the code
that 'meter->max_delta_t' can't have a value large enough to overflow.	 
 net/openvswitch/meter.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index cc08e0403909..4811af859405 100644
--- a/net/openvswitch/meter.c
+++ b/net/openvswitch/meter.c

@@ -646,11 +646,14 @@ bool ovs_meter_execute(struct datapath *dp, struct sk_buff *skb,
 	/* Update all bands and find the one hit with the highest rate. */
 	for (i = 0; i < meter->n_bands; ++i) {
 		long long int max_bucket_size;
+		u32 result;
 
 		band = &meter->bands[i];
 		max_bucket_size = band->burst_size * 1000LL;
 
-		band->bucket += delta_ms * band->rate;
+		WARN_ON(check_mul_overflow(delta_ms, band->rate, &result));
+		band->bucket += result;
+
 		if (band->bucket > max_bucket_size)
 			band->bucket = max_bucket_size;
 

-- 
2.39.5 (Apple Git-154)