[PATCH] ethtool: avoiding integer overflow in ethtool_phys_id()

The value of an arithmetic expression "n * id.data" is subject
to possible overflow due to a failure to cast operands to a larger data
type before performing arithmetic. Added cast of first operand to u64
for avoiding overflow.

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

Fixes: 2adc6edcaec0 ("ethtool: fix error handling in ethtool_phys_id")
Signed-off-by: Maxim Korotkov <redacted>
---
 net/ethtool/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 6a7308de192d..cf87e53c2e74 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c

@@ -2007,7 +2007,7 @@ static int ethtool_phys_id(struct net_device *dev, void __user *useraddr)
 	} else {
 		/* Driver expects to be called at twice the frequency in rc */
 		int n = rc * 2, interval = HZ / n;
-		u64 count = n * id.data, i = 0;
+		u64 count = (u64)n * id.data, i = 0;
 
 		do {
 			rtnl_lock();

-- 
2.17.1