[PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[Maxim Korotkov]

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>
---
 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

Re: [PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[Alexander Lobakin]

From: Maxim Korotkov <korotkov.maxim.s@gmail.com>
Date: Tue, 22 Nov 2022 15:29:01 +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 <korotkov.maxim.s@gmail.com>

Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.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

Some notes to the process, not the code:

1) I asked to add my Reviewed-by to v3 in the previous thread, it's
   mandatory for authors to pick-up all the tags before publishing
   a new revision;
2) when sending v2, v3, ... vN, please have a changelog in the
   commit message or right below those '---' after your SoB, that
   makes it easier to review.

Thanks,
Olek

Re: [PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[Andrew Lunn]

On Tue, Nov 22, 2022 at 03:29:01PM +0300, Maxim Korotkov wrote:
> 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: Andrew Lunn <andrew@lunn.ch>

    Andrew

Re: [PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[Jakub Kicinski]

On Tue, 22 Nov 2022 15:29:01 +0300 Maxim Korotkov wrote:
> 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>

Applying to net-next, pretty sure nobody expects us to support blinking
an LED 4 billion times, at a rate low enough for a human eye to see...
But let's watch the stable bots pick it up anyway.

Re: [PATCH v3] ethtool: avoiding integer overflow in ethtool_phys_id()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 22 Nov 2022 15:29:01 +0300 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [v3] ethtool: avoiding integer overflow in ethtool_phys_id()
    https://git.kernel.org/netdev/net-next/c/64a8f8f7127d

You are awesome, thank you!
-- 
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