[PATCH AUTOSEL 6.1 57/85] ethtool: avoiding integer overflow in ethtool_phys_id()

[Sasha Levin]

From: Maxim Korotkov <korotkov.maxim.s@xxxxxxxxx>

[ Upstream commit 64a8f8f7127da228d59a39e2c5e75f86590f90b4 ]

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@xxxxxxxxx>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@xxxxxxxxx>
Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Link: https://lore.kernel.org/r/20221122122901.22294-1-korotkov.maxim.s@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ethtool/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 57e7238a4136..81fe2422fe58 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2008,7 +2008,8 @@ 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();
-- 
2.35.1