2022-11-22 07:35:16

by Maxim Korotkov

Subject: [PATCH v2] 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 <[email protected]>
---
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..f845e8be4d7c 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

2022-11-22 12:44:26

by Alexander Lobakin

Subject: Re: [PATCH v2] ethtool: avoiding integer overflow in ethtool_phys_id()

From: Maxim Korotkov <[email protected]>
Date: Tue, 22 Nov 2022 09:54:23 +0300

> 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 <[email protected]>
> ---
> 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..f845e8be4d7c 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);

^^

Meh, you forgot to put a space after the comma :s

Other than that (please add it to a v3):

Reviewed-by: Alexander Lobakin <[email protected]>

> + u64 i = 0;
>
> do {
> rtnl_lock();
> --
> 2.17.1

Thanks,
Olek