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. Used macro for multiplication instead
operator for avoiding overflow.

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

Signed-off-by: Maxim Korotkov <korotkov.maxim.s@gmail.com>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20221122122901.22294-1-korotkov.maxim.s@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 99272a67525c55cbf56f39aeb030a014d9e9ae09..c2f1a542e6fa9ccd94ba9c63f707c78439405921 100644 (file)
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2013,7 +2013,8 @@ 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 = mul_u32_u32(n, id.data);
+               u64 i = 0;
 
                do {
                        rtnl_lock();