netdev - [PATCH v3] ethtool: avoiding integer overflow in ethtool_phys

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Message-Id: <20221122122901.22294-1-korotkov.maxim.s@gmail.com>
Date:   Tue, 22 Nov 2022 15:29:01 +0300
From:   Maxim Korotkov <korotkov.maxim.s@...il.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Maxim Korotkov <korotkov.maxim.s@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Guangbin Huang <huangguangbin2@...wei.com>,
        Andrew Lunn <andrew@...n.ch>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        "Keller, Jacob E" <jacob.e.keller@...el.com>,
        Tom Rix <trix@...hat.com>, Marco Bonelli <marco@...eim.net>,
        Edward Cree <ecree@...arflare.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: [PATCH v3] 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@...il.com>
---
 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 6a7308de192d..6b59e7a1c906 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2007,7 +2007,8 @@ 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();
-- 
2.17.1